# Collections

public class **Collections** extends [Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html)  
This class consists exclusively of static methods that operate on or return
collections. It contains polymorphic algorithms that operate on
collections, "wrappers", which return a new collection backed by a
specified collection, and a few other odds and ends.

The methods of this class all throw a NullPointerException
if the collections or class objects provided to them are null.

The documentation for the polymorphic algorithms contained in this class
generally includes a brief description of the *implementation*. Such
descriptions should be regarded as *implementation notes*, rather than
parts of the *specification*. Implementors should feel free to
substitute other algorithms, so long as the specification itself is adhered
to. (For example, the algorithm used by sort does not have to be
a mergesort, but it does have to be *stable*.)

The "destructive" algorithms contained in this class, that is, the
algorithms that modify the collection on which they operate, are specified
to throw UnsupportedOperationException if the collection does not
support the appropriate mutation primitive(s), such as the set
method. These algorithms may, but are not required to, throw this
exception if an invocation would have no effect on the collection. For
example, invoking the sort method on an unmodifiable list that is
already sorted may or may not throw UnsupportedOperationException.

This class is a member of the
[Java Collections Framework](https://developers.google.com/j2objc/javadoc/jre/technotes/guides/collections/index.html).

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Set.html`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html`

### Field Summary

|---|---|---|
| public static final [List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html) | [EMPTY_LIST](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#EMPTY_LIST) | The empty list (immutable). |
| public static final [Map](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html) | [EMPTY_MAP](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#EMPTY_MAP) | The empty map (immutable). |
| public static final [Set](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Set.html) | [EMPTY_SET](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#EMPTY_SET) | The empty set (immutable). |

### Public Method Summary

|---|---|
| static \<T\> boolean | [addAll](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#addAll(java.util.Collection<?%20super%20T>,%20T...))([Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<? super T\> c, T... elements) Adds all of the specified elements to the specified collection. |
| static \<T\> [Queue](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Queue.html)\<T\> | [asLifoQueue](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#asLifoQueue(java.util.Deque<T>))([Deque](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Deque.html)\<T\> deque) Returns a view of a `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Deque.html` as a Last-in-first-out (Lifo) `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Queue.html`. |
| static \<T\> int | [binarySearch](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#binarySearch(java.util.List<?%20extends%20T>,%20T,%20java.util.Comparator<?%20super%20T>))([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<? extends T\> list, T key, [Comparator](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Comparator.html)\<? super T\> c) Searches the specified list for the specified object using the binary search algorithm. |
| static \<T\> int | [binarySearch](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#binarySearch(java.util.List<?%20extends%20java.lang.Comparable<?%20super%20T>>,%20T))([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<? extends [Comparable](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Comparable.html)\<? super T\>\> list, T key) Searches the specified list for the specified object using the binary search algorithm. |
| static \<E\> [Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<E\> | [checkedCollection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#checkedCollection(java.util.Collection<E>,%20java.lang.Class<E>))([Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<E\> c, [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<E\> type) Returns a dynamically typesafe view of the specified collection. |
| static \<E\> [List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<E\> | [checkedList](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#checkedList(java.util.List<E>,%20java.lang.Class<E>))([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<E\> list, [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<E\> type) Returns a dynamically typesafe view of the specified list. |
| static \<K, V\> [Map](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html)\<K, V\> | [checkedMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#checkedMap(java.util.Map<K,%20V>,%20java.lang.Class<K>,%20java.lang.Class<V>))([Map](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html)\<K, V\> m, [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<K\> keyType, [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<V\> valueType) Returns a dynamically typesafe view of the specified map. |
| static \<K, V\> [NavigableMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableMap.html)\<K, V\> | [checkedNavigableMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#checkedNavigableMap(java.util.NavigableMap<K,%20V>,%20java.lang.Class<K>,%20java.lang.Class<V>))([NavigableMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableMap.html)\<K, V\> m, [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<K\> keyType, [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<V\> valueType) Returns a dynamically typesafe view of the specified navigable map. |
| static \<E\> [NavigableSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableSet.html)\<E\> | [checkedNavigableSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#checkedNavigableSet(java.util.NavigableSet<E>,%20java.lang.Class<E>))([NavigableSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableSet.html)\<E\> s, [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<E\> type) Returns a dynamically typesafe view of the specified navigable set. |
| static \<E\> [Queue](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Queue.html)\<E\> | [checkedQueue](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#checkedQueue(java.util.Queue<E>,%20java.lang.Class<E>))([Queue](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Queue.html)\<E\> queue, [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<E\> type) Returns a dynamically typesafe view of the specified queue. |
| static \<E\> [Set](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Set.html)\<E\> | [checkedSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#checkedSet(java.util.Set<E>,%20java.lang.Class<E>))([Set](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Set.html)\<E\> s, [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<E\> type) Returns a dynamically typesafe view of the specified set. |
| static \<K, V\> [SortedMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedMap.html)\<K, V\> | [checkedSortedMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#checkedSortedMap(java.util.SortedMap<K,%20V>,%20java.lang.Class<K>,%20java.lang.Class<V>))([SortedMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedMap.html)\<K, V\> m, [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<K\> keyType, [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<V\> valueType) Returns a dynamically typesafe view of the specified sorted map. |
| static \<E\> [SortedSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedSet.html)\<E\> | [checkedSortedSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#checkedSortedSet(java.util.SortedSet<E>,%20java.lang.Class<E>))([SortedSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedSet.html)\<E\> s, [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<E\> type) Returns a dynamically typesafe view of the specified sorted set. |
| static \<T\> void | [copy](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#copy(java.util.List<?%20super%20T>,%20java.util.List<?%20extends%20T>))([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<? super T\> dest, [List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<? extends T\> src) Copies all of the elements from one list into another. |
| static boolean | [disjoint](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#disjoint(java.util.Collection<?>,%20java.util.Collection<?>))([Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<?\> c1, [Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<?\> c2) Returns `true` if the two specified collections have no elements in common. |
| static \<T\> [Enumeration](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Enumeration.html)\<T\> | [emptyEnumeration](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#emptyEnumeration())() Returns an enumeration that has no elements. |
| static \<T\> [Iterator](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Iterator.html)\<T\> | [emptyIterator](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#emptyIterator())() Returns an iterator that has no elements. |
| final static \<T\> [List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<T\> | [emptyList](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#emptyList())() Returns an empty list (immutable). |
| static \<T\> [ListIterator](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/ListIterator.html)\<T\> | [emptyListIterator](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#emptyListIterator())() Returns a list iterator that has no elements. |
| final static \<K, V\> [Map](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html)\<K, V\> | [emptyMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#emptyMap())() Returns an empty map (immutable). |
| final static \<K, V\> [NavigableMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableMap.html)\<K, V\> | [emptyNavigableMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#emptyNavigableMap())() Returns an empty navigable map (immutable). |
| static \<E\> [NavigableSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableSet.html)\<E\> | [emptyNavigableSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#emptyNavigableSet())() Returns an empty navigable set (immutable). |
| final static \<T\> [Set](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Set.html)\<T\> | [emptySet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#emptySet())() Returns an empty set (immutable). |
| final static \<K, V\> [SortedMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedMap.html)\<K, V\> | [emptySortedMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#emptySortedMap())() Returns an empty sorted map (immutable). |
| static \<E\> [SortedSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedSet.html)\<E\> | [emptySortedSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#emptySortedSet())() Returns an empty sorted set (immutable). |
| static \<T\> [Enumeration](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Enumeration.html)\<T\> | [enumeration](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#enumeration(java.util.Collection<T>))([Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<T\> c) Returns an enumeration over the specified collection. |
| static \<T\> void | [fill](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#fill(java.util.List<?%20super%20T>,%20T))([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<? super T\> list, T obj) Replaces all of the elements of the specified list with the specified element. |
| static int | [frequency](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#frequency(java.util.Collection<?>,%20java.lang.Object))([Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<?\> c, [Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html) o) Returns the number of elements in the specified collection equal to the specified object. |
| static int | [indexOfSubList](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#indexOfSubList(java.util.List<?>,%20java.util.List<?>))([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<?\> source, [List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<?\> target) Returns the starting position of the first occurrence of the specified target list within the specified source list, or -1 if there is no such occurrence. |
| static int | [lastIndexOfSubList](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#lastIndexOfSubList(java.util.List<?>,%20java.util.List<?>))([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<?\> source, [List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<?\> target) Returns the starting position of the last occurrence of the specified target list within the specified source list, or -1 if there is no such occurrence. |
| static \<T\> [ArrayList](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/ArrayList.html)\<T\> | [list](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#list(java.util.Enumeration<T>))([Enumeration](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Enumeration.html)\<T\> e) Returns an array list containing the elements returned by the specified enumeration in the order they are returned by the enumeration. |
| static \<T\> T | [max](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#max(java.util.Collection<?%20extends%20T>,%20java.util.Comparator<?%20super%20T>))([Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<? extends T\> coll, [Comparator](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Comparator.html)\<? super T\> comp) Returns the maximum element of the given collection, according to the order induced by the specified comparator. |
| static \<T extends [Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html) \& [Comparable](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Comparable.html)\<? super T\>\> T | [max](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#max(java.util.Collection<?%20extends%20T>))([Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<? extends T\> coll) Returns the maximum element of the given collection, according to the *natural ordering* of its elements. |
| static \<T extends [Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html) \& [Comparable](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Comparable.html)\<? super T\>\> T | [min](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#min(java.util.Collection<?%20extends%20T>))([Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<? extends T\> coll) Returns the minimum element of the given collection, according to the *natural ordering* of its elements. |
| static \<T\> T | [min](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#min(java.util.Collection<?%20extends%20T>,%20java.util.Comparator<?%20super%20T>))([Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<? extends T\> coll, [Comparator](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Comparator.html)\<? super T\> comp) Returns the minimum element of the given collection, according to the order induced by the specified comparator. |
| static \<T\> [List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<T\> | [nCopies](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#nCopies(int,%20T))(int n, T o) Returns an immutable list consisting of n copies of the specified object. |
| static \<E\> [Set](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Set.html)\<E\> | [newSetFromMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#newSetFromMap(java.util.Map<E,%20java.lang.Boolean>))([Map](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html)\<E, [Boolean](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Boolean.html)\> map) Returns a set backed by the specified map. |
| static \<T\> boolean | [replaceAll](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#replaceAll(java.util.List<T>,%20T,%20T))([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<T\> list, T oldVal, T newVal) Replaces all occurrences of one specified value in a list with another. |
| static void | [reverse](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#reverse(java.util.List<?>))([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<?\> list) Reverses the order of the elements in the specified list. |
| static \<T\> [Comparator](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Comparator.html)\<T\> | [reverseOrder](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#reverseOrder())() Returns a comparator that imposes the reverse of the *natural ordering* on a collection of objects that implement the `Comparable` interface. |
| static \<T\> [Comparator](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Comparator.html)\<T\> | [reverseOrder](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#reverseOrder(java.util.Comparator<T>))([Comparator](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Comparator.html)\<T\> cmp) Returns a comparator that imposes the reverse ordering of the specified comparator. |
| static void | [rotate](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#rotate(java.util.List<?>,%20int))([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<?\> list, int distance) Rotates the elements in the specified list by the specified distance. |
| static void | [shuffle](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#shuffle(java.util.List<?>,%20java.util.Random))([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<?\> list, [Random](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Random.html) rnd) Randomly permute the specified list using the specified source of randomness. |
| static void | [shuffle](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#shuffle(java.util.List<?>))([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<?\> list) Randomly permutes the specified list using a default source of randomness. |
| static \<T\> [Set](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Set.html)\<T\> | [singleton](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#singleton(T))(T o) Returns an immutable set containing only the specified object. |
| static \<T\> [List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<T\> | [singletonList](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#singletonList(T))(T o) Returns an immutable list containing only the specified object. |
| static \<K, V\> [Map](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html)\<K, V\> | [singletonMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#singletonMap(K,%20V))(K key, V value) Returns an immutable map, mapping only the specified key to the specified value. |
| static \<T extends [Comparable](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Comparable.html)\<? super T\>\> void | [sort](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#sort(java.util.List<T>))([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<T\> list) Sorts the specified list into ascending order, according to the {@linkplain Comparable natural ordering} of its elements. |
| static \<T\> void | [sort](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#sort(java.util.List<T>,%20java.util.Comparator<?%20super%20T>))([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<T\> list, [Comparator](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Comparator.html)\<? super T\> c) Sorts the specified list according to the order induced by the specified comparator. |
| static void | [swap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#swap(java.util.List<?>,%20int,%20int))([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<?\> list, int i, int j) Swaps the elements at the specified positions in the specified list. |
| static \<T\> [Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<T\> | [synchronizedCollection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#synchronizedCollection(java.util.Collection<T>))([Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<T\> c) Returns a synchronized (thread-safe) collection backed by the specified collection. |
| static \<T\> [List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<T\> | [synchronizedList](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#synchronizedList(java.util.List<T>))([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<T\> list) Returns a synchronized (thread-safe) list backed by the specified list. |
| static \<K, V\> [Map](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html)\<K, V\> | [synchronizedMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#synchronizedMap(java.util.Map<K,%20V>))([Map](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html)\<K, V\> m) Returns a synchronized (thread-safe) map backed by the specified map. |
| static \<K, V\> [NavigableMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableMap.html)\<K, V\> | [synchronizedNavigableMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#synchronizedNavigableMap(java.util.NavigableMap<K,%20V>))([NavigableMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableMap.html)\<K, V\> m) Returns a synchronized (thread-safe) navigable map backed by the specified navigable map. |
| static \<T\> [NavigableSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableSet.html)\<T\> | [synchronizedNavigableSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#synchronizedNavigableSet(java.util.NavigableSet<T>))([NavigableSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableSet.html)\<T\> s) Returns a synchronized (thread-safe) navigable set backed by the specified navigable set. |
| static \<T\> [Set](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Set.html)\<T\> | [synchronizedSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#synchronizedSet(java.util.Set<T>))([Set](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Set.html)\<T\> s) Returns a synchronized (thread-safe) set backed by the specified set. |
| static \<K, V\> [SortedMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedMap.html)\<K, V\> | [synchronizedSortedMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#synchronizedSortedMap(java.util.SortedMap<K,%20V>))([SortedMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedMap.html)\<K, V\> m) Returns a synchronized (thread-safe) sorted map backed by the specified sorted map. |
| static \<T\> [SortedSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedSet.html)\<T\> | [synchronizedSortedSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#synchronizedSortedSet(java.util.SortedSet<T>))([SortedSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedSet.html)\<T\> s) Returns a synchronized (thread-safe) sorted set backed by the specified sorted set. |
| static \<T\> [Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<T\> | [unmodifiableCollection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#unmodifiableCollection(java.util.Collection<?%20extends%20T>))([Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<? extends T\> c) Returns an unmodifiable view of the specified collection. |
| static \<T\> [List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<T\> | [unmodifiableList](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#unmodifiableList(java.util.List<?%20extends%20T>))([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<? extends T\> list) Returns an unmodifiable view of the specified list. |
| static \<K, V\> [Map](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html)\<K, V\> | [unmodifiableMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#unmodifiableMap(java.util.Map<?%20extends%20K,%20?%20extends%20V>))([Map](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html)\<? extends K, ? extends V\> m) Returns an unmodifiable view of the specified map. |
| static \<K, V\> [NavigableMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableMap.html)\<K, V\> | [unmodifiableNavigableMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#unmodifiableNavigableMap(java.util.NavigableMap<K,%20?%20extends%20V>))([NavigableMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableMap.html)\<K, ? extends V\> m) Returns an unmodifiable view of the specified navigable map. |
| static \<T\> [NavigableSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableSet.html)\<T\> | [unmodifiableNavigableSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#unmodifiableNavigableSet(java.util.NavigableSet<T>))([NavigableSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableSet.html)\<T\> s) Returns an unmodifiable view of the specified navigable set. |
| static \<T\> [Set](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Set.html)\<T\> | [unmodifiableSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#unmodifiableSet(java.util.Set<?%20extends%20T>))([Set](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Set.html)\<? extends T\> s) Returns an unmodifiable view of the specified set. |
| static \<K, V\> [SortedMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedMap.html)\<K, V\> | [unmodifiableSortedMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#unmodifiableSortedMap(java.util.SortedMap<K,%20?%20extends%20V>))([SortedMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedMap.html)\<K, ? extends V\> m) Returns an unmodifiable view of the specified sorted map. |
| static \<T\> [SortedSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedSet.html)\<T\> | [unmodifiableSortedSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#unmodifiableSortedSet(java.util.SortedSet<T>))([SortedSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedSet.html)\<T\> s) Returns an unmodifiable view of the specified sorted set. |

### Inherited Method Summary

From class [java.lang.Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html)

|---|---|
| [Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html) | [clone](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#clone())() Creates and returns a copy of this `Object`. |
| boolean | [equals](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#equals(java.lang.Object))([Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html) obj) Compares this instance with the specified object and indicates if they are equal. |
| void | [finalize](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#finalize())() Invoked when the garbage collector has detected that this instance is no longer reachable. |
| final [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<?\> | [getClass](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#getClass())() Returns the unique instance of `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html` that represents this object's class. |
| int | [hashCode](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#hashCode())() Returns an integer hash code for this object. |
| final void | [notify](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#notify())() Causes a thread which is waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up. |
| final void | [notifyAll](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#notifyAll())() Causes all threads which are waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up. |
| [String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) | [toString](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#toString())() Returns a string containing a concise, human-readable description of this object. |
| final void | [wait](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#wait(long,%20int))(long timeout, int nanos) Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires. |
| final void | [wait](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#wait(long))(long timeout) Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires. |
| final void | [wait](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#wait())() Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object. |

## Fields

#### public static final [List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)
**EMPTY_LIST**

The empty list (immutable). This list is serializable.

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#emptyList()`

#### public static final [Map](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html)
**EMPTY_MAP**

The empty map (immutable). This map is serializable.

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#emptyMap()`

#### public static final [Set](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Set.html)
**EMPTY_SET**

The empty set (immutable). This set is serializable.

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#emptySet()`

## Public Methods

#### public static boolean
**addAll**
([Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<? super T\> c, T... elements)

Adds all of the specified elements to the specified collection.
Elements to be added may be specified individually or as an array.
The behavior of this convenience method is identical to that of
c.addAll(Arrays.asList(elements)), but this method is likely
to run significantly faster under most implementations.

When elements are specified individually, this method provides a
convenient way to add a few elements to an existing collection:

```
     Collections.addAll(flavors, "Peaches 'n Plutonium", "Rocky Racoon");
 
```

<br />

##### Parameters

| c | the collection into which elements are to be inserted |
| elements | the elements to insert into c |
|---|---|

##### Returns

- true if the collection changed as a result of the call

##### Throws

| [UnsupportedOperationException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/UnsupportedOperationException.html) | if c does not support the add operation |
| [NullPointerException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/NullPointerException.html) | if elements contains one or more null values and c does not permit null elements, or if c or elements are null |
| [IllegalArgumentException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/IllegalArgumentException.html) | if some property of a value in elements prevents it from being added to c |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html#addAll(java.util.Collection<?%20extends%20E>)`

#### public static [Queue](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Queue.html)\<T\>
**asLifoQueue**
([Deque](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Deque.html)\<T\> deque)

Returns a view of a `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Deque.html` as a Last-in-first-out (Lifo)
`https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Queue.html`. Method add is mapped to push,
remove is mapped to pop and so on. This
view can be useful when you would like to use a method
requiring a Queue but you need Lifo ordering.

Each method invocation on the queue returned by this method
results in exactly one method invocation on the backing deque, with
one exception. The `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html#addAll(java.util.Collection<?%20extends%20E>)` method is
implemented as a sequence of `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Deque.html#addFirst(E)`
invocations on the backing deque.

##### Parameters

| deque | the deque |
|---|---|

##### Returns

- the queue

#### public static int
**binarySearch**
([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<? extends T\> list, T key, [Comparator](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Comparator.html)\<? super T\> c)

Searches the specified list for the specified object using the binary
search algorithm. The list must be sorted into ascending order
according to the specified comparator (as by the
`https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#sort(java.util.List<T>,%20java.util.Comparator<?%20super%20T>)`
method), prior to making this call. If it is
not sorted, the results are undefined. If the list contains multiple
elements equal to the specified object, there is no guarantee which one
will be found.

This method runs in log(n) time for a "random access" list (which
provides near-constant-time positional access). If the specified list
does not implement the `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/RandomAccess.html` interface and is large,
this method will do an iterator-based binary search that performs
O(n) link traversals and O(log n) element comparisons.

##### Parameters

| list | the list to be searched. |
| key | the key to be searched for. |
| c | the comparator by which the list is ordered. A null value indicates that the elements' {@linkplain Comparable natural ordering} should be used. |
|---|---|

##### Returns

- the index of the search key, if it is contained in the list; otherwise, (-(*insertion point*) - 1). The *insertion point* is defined as the point at which the key would be inserted into the list: the index of the first element greater than the key, or list.size() if all elements in the list are less than the specified key. Note that this guarantees that the return value will be \>= 0 if and only if the key is found.

##### Throws

| [ClassCastException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ClassCastException.html) | if the list contains elements that are not *mutually comparable* using the specified comparator, or the search key is not mutually comparable with the elements of the list using this comparator. |
|---|---|

#### public static int
**binarySearch**
([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<? extends [Comparable](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Comparable.html)\<? super T\>\> list, T key)

Searches the specified list for the specified object using the binary
search algorithm. The list must be sorted into ascending order
according to the {@linkplain Comparable natural ordering} of its
elements (as by the `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#sort(java.util.List<T>)` method) prior to making this
call. If it is not sorted, the results are undefined. If the list
contains multiple elements equal to the specified object, there is no
guarantee which one will be found.

This method runs in log(n) time for a "random access" list (which
provides near-constant-time positional access). If the specified list
does not implement the `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/RandomAccess.html` interface and is large,
this method will do an iterator-based binary search that performs
O(n) link traversals and O(log n) element comparisons.

##### Parameters

| list | the list to be searched. |
| key | the key to be searched for. |
|---|---|

##### Returns

- the index of the search key, if it is contained in the list; otherwise, (-(*insertion point*) - 1). The *insertion point* is defined as the point at which the key would be inserted into the list: the index of the first element greater than the key, or list.size() if all elements in the list are less than the specified key. Note that this guarantees that the return value will be \>= 0 if and only if the key is found.

##### Throws

| [ClassCastException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ClassCastException.html) | if the list contains elements that are not *mutually comparable* (for example, strings and integers), or the search key is not mutually comparable with the elements of the list. |
|---|---|

#### public static [Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<E\>
**checkedCollection**
([Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<E\> c, [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<E\> type)

Returns a dynamically typesafe view of the specified collection.
Any attempt to insert an element of the wrong type will result in an
immediate `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ClassCastException.html`. Assuming a collection
contains no incorrectly typed elements prior to the time a
dynamically typesafe view is generated, and that all subsequent
access to the collection takes place through the view, it is
*guaranteed* that the collection cannot contain an incorrectly
typed element.

The generics mechanism in the language provides compile-time
(static) type checking, but it is possible to defeat this mechanism
with unchecked casts. Usually this is not a problem, as the compiler
issues warnings on all such unchecked operations. There are, however,
times when static type checking alone is not sufficient. For example,
suppose a collection is passed to a third-party library and it is
imperative that the library code not corrupt the collection by
inserting an element of the wrong type.

Another use of dynamically typesafe views is debugging. Suppose a
program fails with a `ClassCastException`, indicating that an
incorrectly typed element was put into a parameterized collection.
Unfortunately, the exception can occur at any time after the erroneous
element is inserted, so it typically provides little or no information
as to the real source of the problem. If the problem is reproducible,
one can quickly determine its source by temporarily modifying the
program to wrap the collection with a dynamically typesafe view.
For example, this declaration:

     Collection<String> c = new HashSet<>();
     
may be replaced temporarily by this one:

     Collection<String> c = Collections.checkedCollection(
             new HashSet<>(), String.class);
     
Running the program again will cause it to fail at the point where an incorrectly typed element is inserted into the collection, clearly identifying the source of the problem. Once the problem is fixed, the modified declaration may be reverted back to the original.

The returned collection does *not* pass the hashCode and equals
operations through to the backing collection, but relies on
`Object`'s `equals` and `hashCode` methods. This
is necessary to preserve the contracts of these operations in the case
that the backing collection is a set or a list.

The returned collection will be serializable if the specified
collection is serializable.

Since `null` is considered to be a value of any reference
type, the returned collection permits insertion of null elements
whenever the backing collection does.

##### Parameters

| c | the collection for which a dynamically typesafe view is to be returned |
| type | the type of element that `c` is permitted to hold |
|---|---|

##### Returns

- a dynamically typesafe view of the specified collection

#### public static [List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<E\>
**checkedList**
([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<E\> list, [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<E\> type)

Returns a dynamically typesafe view of the specified list.
Any attempt to insert an element of the wrong type will result in
an immediate `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ClassCastException.html`. Assuming a list contains
no incorrectly typed elements prior to the time a dynamically typesafe
view is generated, and that all subsequent access to the list
takes place through the view, it is *guaranteed* that the
list cannot contain an incorrectly typed element.

A discussion of the use of dynamically typesafe views may be
found in the documentation for the `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#checkedCollection(java.util.Collection<E>,%20java.lang.Class<E>)` method.

The returned list will be serializable if the specified list
is serializable.

Since `null` is considered to be a value of any reference
type, the returned list permits insertion of null elements whenever
the backing list does.

##### Parameters

| list | the list for which a dynamically typesafe view is to be returned |
| type | the type of element that `list` is permitted to hold |
|---|---|

##### Returns

- a dynamically typesafe view of the specified list

#### public static [Map](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html)\<K, V\>
**checkedMap**
([Map](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html)\<K, V\> m, [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<K\> keyType, [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<V\> valueType)

Returns a dynamically typesafe view of the specified map.
Any attempt to insert a mapping whose key or value have the wrong
type will result in an immediate `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ClassCastException.html`.
Similarly, any attempt to modify the value currently associated with
a key will result in an immediate `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ClassCastException.html`,
whether the modification is attempted directly through the map
itself, or through a `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.Entry.html` instance obtained from the
map's `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html#entrySet()` view.

Assuming a map contains no incorrectly typed keys or values
prior to the time a dynamically typesafe view is generated, and
that all subsequent access to the map takes place through the view
(or one of its collection views), it is *guaranteed* that the
map cannot contain an incorrectly typed key or value.

A discussion of the use of dynamically typesafe views may be
found in the documentation for the `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#checkedCollection(java.util.Collection<E>,%20java.lang.Class<E>)` method.

The returned map will be serializable if the specified map is
serializable.

Since `null` is considered to be a value of any reference
type, the returned map permits insertion of null keys or values
whenever the backing map does.

##### Parameters

| m | the map for which a dynamically typesafe view is to be returned |
| keyType | the type of key that `m` is permitted to hold |
| valueType | the type of value that `m` is permitted to hold |
|---|---|

##### Returns

- a dynamically typesafe view of the specified map

#### public static [NavigableMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableMap.html)\<K, V\>
**checkedNavigableMap**
([NavigableMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableMap.html)\<K, V\> m, [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<K\> keyType, [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<V\> valueType)

Returns a dynamically typesafe view of the specified navigable map.
Any attempt to insert a mapping whose key or value have the wrong
type will result in an immediate `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ClassCastException.html`.
Similarly, any attempt to modify the value currently associated with
a key will result in an immediate `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ClassCastException.html`,
whether the modification is attempted directly through the map
itself, or through a `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.Entry.html` instance obtained from the
map's `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html#entrySet()` view.

Assuming a map contains no incorrectly typed keys or values
prior to the time a dynamically typesafe view is generated, and
that all subsequent access to the map takes place through the view
(or one of its collection views), it is *guaranteed* that the
map cannot contain an incorrectly typed key or value.

A discussion of the use of dynamically typesafe views may be
found in the documentation for the `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#checkedCollection(java.util.Collection<E>,%20java.lang.Class<E>)` method.

The returned map will be serializable if the specified map is
serializable.

Since `null` is considered to be a value of any reference
type, the returned map permits insertion of null keys or values
whenever the backing map does.

##### Parameters

| m | the map for which a dynamically typesafe view is to be returned |
| keyType | the type of key that `m` is permitted to hold |
| valueType | the type of value that `m` is permitted to hold |
|---|---|

##### Returns

- a dynamically typesafe view of the specified map

#### public static [NavigableSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableSet.html)\<E\>
**checkedNavigableSet**
([NavigableSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableSet.html)\<E\> s, [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<E\> type)

Returns a dynamically typesafe view of the specified navigable set.
Any attempt to insert an element of the wrong type will result in an
immediate `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ClassCastException.html`. Assuming a navigable set
contains no incorrectly typed elements prior to the time a
dynamically typesafe view is generated, and that all subsequent
access to the navigable set takes place through the view, it is
*guaranteed* that the navigable set cannot contain an incorrectly
typed element.

A discussion of the use of dynamically typesafe views may be
found in the documentation for the `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#checkedCollection(java.util.Collection<E>,%20java.lang.Class<E>)` method.

The returned navigable set will be serializable if the specified
navigable set is serializable.

Since `null` is considered to be a value of any reference
type, the returned navigable set permits insertion of null elements
whenever the backing sorted set does.

##### Parameters

| s | the navigable set for which a dynamically typesafe view is to be returned |
| type | the type of element that `s` is permitted to hold |
|---|---|

##### Returns

- a dynamically typesafe view of the specified navigable set

#### public static [Queue](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Queue.html)\<E\>
**checkedQueue**
([Queue](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Queue.html)\<E\> queue, [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<E\> type)

Returns a dynamically typesafe view of the specified queue.
Any attempt to insert an element of the wrong type will result in
an immediate `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ClassCastException.html`. Assuming a queue contains
no incorrectly typed elements prior to the time a dynamically typesafe
view is generated, and that all subsequent access to the queue
takes place through the view, it is *guaranteed* that the
queue cannot contain an incorrectly typed element.

A discussion of the use of dynamically typesafe views may be
found in the documentation for the `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#checkedCollection(java.util.Collection<E>,%20java.lang.Class<E>)` method.

The returned queue will be serializable if the specified queue
is serializable.

Since `null` is considered to be a value of any reference
type, the returned queue permits insertion of `null` elements
whenever the backing queue does.

##### Parameters

| queue | the queue for which a dynamically typesafe view is to be returned |
| type | the type of element that `queue` is permitted to hold |
|---|---|

##### Returns

- a dynamically typesafe view of the specified queue

#### public static [Set](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Set.html)\<E\>
**checkedSet**
([Set](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Set.html)\<E\> s, [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<E\> type)

Returns a dynamically typesafe view of the specified set.
Any attempt to insert an element of the wrong type will result in
an immediate `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ClassCastException.html`. Assuming a set contains
no incorrectly typed elements prior to the time a dynamically typesafe
view is generated, and that all subsequent access to the set
takes place through the view, it is *guaranteed* that the
set cannot contain an incorrectly typed element.

A discussion of the use of dynamically typesafe views may be
found in the documentation for the `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#checkedCollection(java.util.Collection<E>,%20java.lang.Class<E>)` method.

The returned set will be serializable if the specified set is
serializable.

Since `null` is considered to be a value of any reference
type, the returned set permits insertion of null elements whenever
the backing set does.

##### Parameters

| s | the set for which a dynamically typesafe view is to be returned |
| type | the type of element that `s` is permitted to hold |
|---|---|

##### Returns

- a dynamically typesafe view of the specified set

#### public static [SortedMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedMap.html)\<K, V\>
**checkedSortedMap**
([SortedMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedMap.html)\<K, V\> m, [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<K\> keyType, [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<V\> valueType)

Returns a dynamically typesafe view of the specified sorted map.
Any attempt to insert a mapping whose key or value have the wrong
type will result in an immediate `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ClassCastException.html`.
Similarly, any attempt to modify the value currently associated with
a key will result in an immediate `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ClassCastException.html`,
whether the modification is attempted directly through the map
itself, or through a `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.Entry.html` instance obtained from the
map's `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html#entrySet()` view.

Assuming a map contains no incorrectly typed keys or values
prior to the time a dynamically typesafe view is generated, and
that all subsequent access to the map takes place through the view
(or one of its collection views), it is *guaranteed* that the
map cannot contain an incorrectly typed key or value.

A discussion of the use of dynamically typesafe views may be
found in the documentation for the `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#checkedCollection(java.util.Collection<E>,%20java.lang.Class<E>)` method.

The returned map will be serializable if the specified map is
serializable.

Since `null` is considered to be a value of any reference
type, the returned map permits insertion of null keys or values
whenever the backing map does.

##### Parameters

| m | the map for which a dynamically typesafe view is to be returned |
| keyType | the type of key that `m` is permitted to hold |
| valueType | the type of value that `m` is permitted to hold |
|---|---|

##### Returns

- a dynamically typesafe view of the specified map

#### public static [SortedSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedSet.html)\<E\>
**checkedSortedSet**
([SortedSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedSet.html)\<E\> s, [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<E\> type)

Returns a dynamically typesafe view of the specified sorted set.
Any attempt to insert an element of the wrong type will result in an
immediate `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ClassCastException.html`. Assuming a sorted set
contains no incorrectly typed elements prior to the time a
dynamically typesafe view is generated, and that all subsequent
access to the sorted set takes place through the view, it is
*guaranteed* that the sorted set cannot contain an incorrectly
typed element.

A discussion of the use of dynamically typesafe views may be
found in the documentation for the `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#checkedCollection(java.util.Collection<E>,%20java.lang.Class<E>)` method.

The returned sorted set will be serializable if the specified sorted
set is serializable.

Since `null` is considered to be a value of any reference
type, the returned sorted set permits insertion of null elements
whenever the backing sorted set does.

##### Parameters

| s | the sorted set for which a dynamically typesafe view is to be returned |
| type | the type of element that `s` is permitted to hold |
|---|---|

##### Returns

- a dynamically typesafe view of the specified sorted set

#### public static void
**copy**
([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<? super T\> dest, [List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<? extends T\> src)

Copies all of the elements from one list into another. After the
operation, the index of each copied element in the destination list
will be identical to its index in the source list. The destination
list must be at least as long as the source list. If it is longer, the
remaining elements in the destination list are unaffected.


This method runs in linear time.

##### Parameters

| dest | The destination list. |
| src | The source list. |
|---|---|

##### Throws

| [IndexOutOfBoundsException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/IndexOutOfBoundsException.html) | if the destination list is too small to contain the entire source List. |
| [UnsupportedOperationException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/UnsupportedOperationException.html) | if the destination list's list-iterator does not support the set operation. |
|---|---|

#### public static boolean
**disjoint**
([Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<?\> c1, [Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<?\> c2)

Returns `true` if the two specified collections have no
elements in common.

Care must be exercised if this method is used on collections that
do not comply with the general contract for `Collection`.
Implementations may elect to iterate over either collection and test
for containment in the other collection (or to perform any equivalent
computation). If either collection uses a nonstandard equality test
(as does a `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedSet.html` whose ordering is not *compatible with
equals* , or the key set of an `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/IdentityHashMap.html`), both
collections must use the same nonstandard equality test, or the
result of this method is undefined.

Care must also be exercised when using collections that have
restrictions on the elements that they may contain. Collection
implementations are allowed to throw exceptions for any operation
involving elements they deem ineligible. For absolute safety the
specified collections should contain only elements which are
eligible elements for both collections.

Note that it is permissible to pass the same collection in both
parameters, in which case the method will return `true` if and
only if the collection is empty.

##### Parameters

| c1 | a collection |
| c2 | a collection |
|---|---|

##### Returns

- `true` if the two specified collections have no elements in common.

##### Throws

| [NullPointerException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/NullPointerException.html) | if either collection is `null`. |
| [NullPointerException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/NullPointerException.html) | if one collection contains a `null` element and `null` is not an eligible element for the other collection. ([optional](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection#optional-restrictions)) |
| [ClassCastException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ClassCastException.html) | if one collection contains an element that is of a type which is ineligible for the other collection. ([optional](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection#optional-restrictions)) |
|---|---|

#### public static [Enumeration](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Enumeration.html)\<T\>
**emptyEnumeration**
()

Returns an enumeration that has no elements. More precisely,

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Enumeration.html#hasMoreElements()` always returns `false`.
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Enumeration.html#nextElement()` always throws `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NoSuchElementException.html`.

Implementations of this method are permitted, but not
required, to return the same object from multiple invocations.

##### Returns

- an empty enumeration

#### public static [Iterator](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Iterator.html)\<T\>
**emptyIterator**
()

Returns an iterator that has no elements. More precisely,

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Iterator.html#hasNext()` always returns `false`.
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Iterator.html#next()` always throws `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NoSuchElementException.html`.
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Iterator.html#remove()` always throws `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/IllegalStateException.html`.

Implementations of this method are permitted, but not
required, to return the same object from multiple invocations.

##### Returns

- an empty iterator

#### public static final [List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<T\>
**emptyList**
()

Returns an empty list (immutable). This list is serializable.

This example illustrates the type-safe way to obtain an empty list:

```
     List<String> s = Collections.emptyList();
 
```

<br />

##### Returns

- an empty immutable list

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#EMPTY_LIST`

#### public static [ListIterator](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/ListIterator.html)\<T\>
**emptyListIterator**
()

Returns a list iterator that has no elements. More precisely,

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Iterator.html#hasNext()` and `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/ListIterator.html#hasPrevious()` always return `false`.
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Iterator.html#next()` and `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/ListIterator.html#previous()` always throw `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NoSuchElementException.html`.
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Iterator.html#remove()` and `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/ListIterator.html#set(E)` always throw `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/IllegalStateException.html`.
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/ListIterator.html#add(E)` always throws `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/UnsupportedOperationException.html`.
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/ListIterator.html#nextIndex()` always returns `0`.
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/ListIterator.html#previousIndex()` always returns `-1`.

Implementations of this method are permitted, but not
required, to return the same object from multiple invocations.

##### Returns

- an empty list iterator

#### public static final [Map](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html)\<K, V\>
**emptyMap**
()

Returns an empty map (immutable). This map is serializable.

This example illustrates the type-safe way to obtain an empty map:

```
     Map<String, Date> s = Collections.emptyMap();
 
```

<br />

##### Returns

- an empty map

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#EMPTY_MAP`

#### public static final [NavigableMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableMap.html)\<K, V\>
**emptyNavigableMap**
()

Returns an empty navigable map (immutable). This map is serializable.

This example illustrates the type-safe way to obtain an empty map:

     NavigableMap<String, Date> s = Collections.emptyNavigableMap();
     
<br />

##### Returns

- an empty navigable map

#### public static [NavigableSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableSet.html)\<E\>
**emptyNavigableSet**
()

Returns an empty navigable set (immutable). This set is serializable.

This example illustrates the type-safe way to obtain an empty
navigable set:

     NavigableSet<String> s = Collections.emptyNavigableSet();
     
<br />

##### Returns

- the empty navigable set

#### public static final [Set](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Set.html)\<T\>
**emptySet**
()

Returns an empty set (immutable). This set is serializable.
Unlike the like-named field, this method is parameterized.

This example illustrates the type-safe way to obtain an empty set:

```
     Set<String> s = Collections.emptySet();
 
```

<br />

##### Returns

- the empty set

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#EMPTY_SET`

#### public static final [SortedMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedMap.html)\<K, V\>
**emptySortedMap**
()

Returns an empty sorted map (immutable). This map is serializable.

This example illustrates the type-safe way to obtain an empty map:

     SortedMap<String, Date> s = Collections.emptySortedMap();
     
<br />

##### Returns

- an empty sorted map

#### public static [SortedSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedSet.html)\<E\>
**emptySortedSet**
()

Returns an empty sorted set (immutable). This set is serializable.

This example illustrates the type-safe way to obtain an empty
sorted set:

     SortedSet<String> s = Collections.emptySortedSet();
     
<br />

##### Returns

- the empty sorted set

#### public static [Enumeration](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Enumeration.html)\<T\>
**enumeration**
([Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<T\> c)

Returns an enumeration over the specified collection. This provides
interoperability with legacy APIs that require an enumeration
as input.

##### Parameters

| c | the collection for which an enumeration is to be returned. |
|---|---|

##### Returns

- an enumeration over the specified collection.

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Enumeration.html`

#### public static void
**fill**
([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<? super T\> list, T obj)

Replaces all of the elements of the specified list with the specified
element.


This method runs in linear time.

##### Parameters

| list | the list to be filled with the specified element. |
| obj | The element with which to fill the specified list. |
|---|---|

##### Throws

| [UnsupportedOperationException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/UnsupportedOperationException.html) | if the specified list or its list-iterator does not support the set operation. |
|---|---|

#### public static int
**frequency**
([Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<?\> c, [Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html) o)

Returns the number of elements in the specified collection equal to the
specified object. More formally, returns the number of elements
e in the collection such that
(o == null ? e == null : o.equals(e)).

##### Parameters

| c | the collection in which to determine the frequency of o |
| o | the object whose frequency is to be determined |
|---|---|

##### Returns

- the number of elements in `c` equal to `o`

##### Throws

| [NullPointerException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/NullPointerException.html) | if c is null |
|---|---|

#### public static int
**indexOfSubList**
([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<?\> source, [List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<?\> target)

Returns the starting position of the first occurrence of the specified
target list within the specified source list, or -1 if there is no
such occurrence. More formally, returns the lowest index i
such that `source.subList(i, i+target.size()).equals(target)`,
or -1 if there is no such index. (Returns -1 if
`target.size() > source.size()`)

This implementation uses the "brute force" technique of scanning
over the source list, looking for a match with the target at each
location in turn.

##### Parameters

| source | the list in which to search for the first occurrence of target. |
| target | the list to search for as a subList of source. |
|---|---|

##### Returns

- the starting position of the first occurrence of the specified target list within the specified source list, or -1 if there is no such occurrence.

#### public static int
**lastIndexOfSubList**
([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<?\> source, [List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<?\> target)

Returns the starting position of the last occurrence of the specified
target list within the specified source list, or -1 if there is no such
occurrence. More formally, returns the highest index i
such that `source.subList(i, i+target.size()).equals(target)`,
or -1 if there is no such index. (Returns -1 if
`target.size() > source.size()`)

This implementation uses the "brute force" technique of iterating
over the source list, looking for a match with the target at each
location in turn.

##### Parameters

| source | the list in which to search for the last occurrence of target. |
| target | the list to search for as a subList of source. |
|---|---|

##### Returns

- the starting position of the last occurrence of the specified target list within the specified source list, or -1 if there is no such occurrence.

#### public static [ArrayList](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/ArrayList.html)\<T\>
**list**
([Enumeration](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Enumeration.html)\<T\> e)

Returns an array list containing the elements returned by the
specified enumeration in the order they are returned by the
enumeration. This method provides interoperability between
legacy APIs that return enumerations and new APIs that require
collections.

##### Parameters

| e | enumeration providing elements for the returned array list |
|---|---|

##### Returns

- an array list containing the elements returned by the specified enumeration.

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Enumeration.html`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/ArrayList.html`

#### public static T
**max**
([Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<? extends T\> coll, [Comparator](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Comparator.html)\<? super T\> comp)

Returns the maximum element of the given collection, according to the
order induced by the specified comparator. All elements in the
collection must be *mutually comparable* by the specified
comparator (that is, comp.compare(e1, e2) must not throw a
ClassCastException for any elements e1 and
e2 in the collection).


This method iterates over the entire collection, hence it requires
time proportional to the size of the collection.

##### Parameters

| coll | the collection whose maximum element is to be determined. |
| comp | the comparator with which to determine the maximum element. A null value indicates that the elements' *natural ordering* should be used. |
|---|---|

##### Returns

- the maximum element of the given collection, according to the specified comparator.

##### Throws

| [ClassCastException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ClassCastException.html) | if the collection contains elements that are not *mutually comparable* using the specified comparator. |
| [NoSuchElementException](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NoSuchElementException.html) | if the collection is empty. |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Comparable.html`

#### public static T
**max**
([Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<? extends T\> coll)

Returns the maximum element of the given collection, according to the
*natural ordering* of its elements. All elements in the
collection must implement the Comparable interface.
Furthermore, all elements in the collection must be *mutually comparable* (that is, e1.compareTo(e2) must not throw a
ClassCastException for any elements e1 and
e2 in the collection).


This method iterates over the entire collection, hence it requires
time proportional to the size of the collection.

##### Parameters

| coll | the collection whose maximum element is to be determined. |
|---|---|

##### Returns

- the maximum element of the given collection, according to the *natural ordering* of its elements.

##### Throws

| [ClassCastException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ClassCastException.html) | if the collection contains elements that are not *mutually comparable* (for example, strings and integers). |
| [NoSuchElementException](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NoSuchElementException.html) | if the collection is empty. |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Comparable.html`

#### public static T
**min**
([Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<? extends T\> coll)

Returns the minimum element of the given collection, according to the
*natural ordering* of its elements. All elements in the
collection must implement the Comparable interface.
Furthermore, all elements in the collection must be *mutually comparable* (that is, e1.compareTo(e2) must not throw a
ClassCastException for any elements e1 and
e2 in the collection).


This method iterates over the entire collection, hence it requires
time proportional to the size of the collection.

##### Parameters

| coll | the collection whose minimum element is to be determined. |
|---|---|

##### Returns

- the minimum element of the given collection, according to the *natural ordering* of its elements.

##### Throws

| [ClassCastException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ClassCastException.html) | if the collection contains elements that are not *mutually comparable* (for example, strings and integers). |
| [NoSuchElementException](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NoSuchElementException.html) | if the collection is empty. |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Comparable.html`

#### public static T
**min**
([Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<? extends T\> coll, [Comparator](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Comparator.html)\<? super T\> comp)

Returns the minimum element of the given collection, according to the
order induced by the specified comparator. All elements in the
collection must be *mutually comparable* by the specified
comparator (that is, comp.compare(e1, e2) must not throw a
ClassCastException for any elements e1 and
e2 in the collection).


This method iterates over the entire collection, hence it requires
time proportional to the size of the collection.

##### Parameters

| coll | the collection whose minimum element is to be determined. |
| comp | the comparator with which to determine the minimum element. A null value indicates that the elements' *natural ordering* should be used. |
|---|---|

##### Returns

- the minimum element of the given collection, according to the specified comparator.

##### Throws

| [ClassCastException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ClassCastException.html) | if the collection contains elements that are not *mutually comparable* using the specified comparator. |
| [NoSuchElementException](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NoSuchElementException.html) | if the collection is empty. |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Comparable.html`

#### public static [List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<T\>
**nCopies**
(int n, T o)

Returns an immutable list consisting of n copies of the
specified object. The newly allocated data object is tiny (it contains
a single reference to the data object). This method is useful in
combination with the List.addAll method to grow lists.
The returned list is serializable.

##### Parameters

| n | the number of elements in the returned list. |
| o | the element to appear repeatedly in the returned list. |
|---|---|

##### Returns

- an immutable list consisting of n copies of the specified object.

##### Throws

| [IllegalArgumentException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/IllegalArgumentException.html) | if `n < 0` |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html#addAll(java.util.Collection<?%20extends%20E>)`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html#addAll(int,%20java.util.Collection<?%20extends%20E>)`

#### public static [Set](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Set.html)\<E\>
**newSetFromMap**
([Map](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html)\<E, [Boolean](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Boolean.html)\> map)

Returns a set backed by the specified map. The resulting set displays
the same ordering, concurrency, and performance characteristics as the
backing map. In essence, this factory method provides a `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Set.html`
implementation corresponding to any `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html` implementation. There
is no need to use this method on a `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html` implementation that
already has a corresponding `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Set.html` implementation (such as `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/HashMap.html` or `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/TreeMap.html`).

Each method invocation on the set returned by this method results in
exactly one method invocation on the backing map or its keySet
view, with one exception. The addAll method is implemented
as a sequence of put invocations on the backing map.

The specified map must be empty at the time this method is invoked,
and should not be accessed directly after this method returns. These
conditions are ensured if the map is created empty, passed directly
to this method, and no reference to the map is retained, as illustrated
in the following code fragment:

```
    Set<Object> weakHashSet = Collections.newSetFromMap(
        new WeakHashMap<Object, Boolean>());
 
```

<br />

##### Parameters

| map | the backing map |
|---|---|

##### Returns

- the set backed by the map

##### Throws

| [IllegalArgumentException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/IllegalArgumentException.html) | if map is not empty |
|---|---|

#### public static boolean
**replaceAll**
([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<T\> list, T oldVal, T newVal)

Replaces all occurrences of one specified value in a list with another.
More formally, replaces with newVal each element e
in list such that
(oldVal==null ? e==null : oldVal.equals(e)).
(This method has no effect on the size of the list.)

##### Parameters

| list | the list in which replacement is to occur. |
| oldVal | the old value to be replaced. |
| newVal | the new value with which oldVal is to be replaced. |
|---|---|

##### Returns

- true if list contained one or more elements e such that (oldVal==null ? e==null : oldVal.equals(e)).

##### Throws

| [UnsupportedOperationException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/UnsupportedOperationException.html) | if the specified list or its list-iterator does not support the set operation. |
|---|---|

#### public static void
**reverse**
([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<?\> list)

Reverses the order of the elements in the specified list.


This method runs in linear time.

##### Parameters

| list | the list whose elements are to be reversed. |
|---|---|

##### Throws

| [UnsupportedOperationException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/UnsupportedOperationException.html) | if the specified list or its list-iterator does not support the set operation. |
|---|---|

#### public static [Comparator](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Comparator.html)\<T\>
**reverseOrder**
()

Returns a comparator that imposes the reverse of the *natural
ordering* on a collection of objects that implement the
`Comparable` interface. (The natural ordering is the ordering
imposed by the objects' own `compareTo` method.) This enables a
simple idiom for sorting (or maintaining) collections (or arrays) of
objects that implement the `Comparable` interface in
reverse-natural-order. For example, suppose `a` is an array of
strings. Then:

```
          Arrays.sort(a, Collections.reverseOrder());
 
```
sorts the array in reverse-lexicographic (alphabetical) order.


The returned comparator is serializable.

##### Returns

- A comparator that imposes the reverse of the *natural ordering* on a collection of objects that implement the Comparable interface.

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Comparable.html`

#### public static [Comparator](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Comparator.html)\<T\>
**reverseOrder**
([Comparator](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Comparator.html)\<T\> cmp)

Returns a comparator that imposes the reverse ordering of the specified
comparator. If the specified comparator is `null`, this method is
equivalent to `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#reverseOrder()` (in other words, it returns a
comparator that imposes the reverse of the *natural ordering* on
a collection of objects that implement the Comparable interface).

The returned comparator is serializable (assuming the specified
comparator is also serializable or `null`).

##### Parameters

| cmp | a comparator who's ordering is to be reversed by the returned comparator or `null` |
|---|---|

##### Returns

- A comparator that imposes the reverse ordering of the specified comparator.

#### public static void
**rotate**
([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<?\> list, int distance)

Rotates the elements in the specified list by the specified distance.
After calling this method, the element at index i will be
the element previously at index (i - distance) mod
list.size(), for all values of i between 0
and list.size()-1, inclusive. (This method has no effect on
the size of the list.)

For example, suppose list comprises \[t, a, n, k, s\].
After invoking Collections.rotate(list, 1) (or
Collections.rotate(list, -4)), list will comprise
\[s, t, a, n, k\].

Note that this method can usefully be applied to sublists to
move one or more elements within a list while preserving the
order of the remaining elements. For example, the following idiom
moves the element at index j forward to position
k (which must be greater than or equal to j):

```
     Collections.rotate(list.subList(j, k+1), -1);
 
```
To make this concrete, suppose list comprises \[a, b, c, d, e\]. To move the element at index 1 (b) forward two positions, perform the following invocation:

```
     Collections.rotate(l.subList(1, 4), -1);
 
```
The resulting list is \[a, c, d, b, e\].

To move more than one element forward, increase the absolute value
of the rotation distance. To move elements backward, use a positive
shift distance.

If the specified list is small or implements the `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/RandomAccess.html` interface, this implementation exchanges the first
element into the location it should go, and then repeatedly exchanges
the displaced element into the location it should go until a displaced
element is swapped into the first element. If necessary, the process
is repeated on the second and successive elements, until the rotation
is complete. If the specified list is large and doesn't implement the
RandomAccess interface, this implementation breaks the
list into two sublist views around index -distance mod size.
Then the `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collections.html#reverse(java.util.List<?>)` method is invoked on each sublist view,
and finally it is invoked on the entire list. For a more complete
description of both algorithms, see Section 2.3 of Jon Bentley's
*Programming Pearls* (Addison-Wesley, 1986).

##### Parameters

| list | the list to be rotated. |
| distance | the distance to rotate the list. There are no constraints on this value; it may be zero, negative, or greater than list.size(). |
|---|---|

##### Throws

| [UnsupportedOperationException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/UnsupportedOperationException.html) | if the specified list or its list-iterator does not support the set operation. |
|---|---|

#### public static void
**shuffle**
([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<?\> list, [Random](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Random.html) rnd)

Randomly permute the specified list using the specified source of
randomness. All permutations occur with equal likelihood
assuming that the source of randomness is fair.


This implementation traverses the list backwards, from the last element
up to the second, repeatedly swapping a randomly selected element into
the "current position". Elements are randomly selected from the
portion of the list that runs from the first element to the current
position, inclusive.


This method runs in linear time. If the specified list does not
implement the `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/RandomAccess.html` interface and is large, this
implementation dumps the specified list into an array before shuffling
it, and dumps the shuffled array back into the list. This avoids the
quadratic behavior that would result from shuffling a "sequential
access" list in place.

##### Parameters

| list | the list to be shuffled. |
| rnd | the source of randomness to use to shuffle the list. |
|---|---|

##### Throws

| [UnsupportedOperationException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/UnsupportedOperationException.html) | if the specified list or its list-iterator does not support the set operation. |
|---|---|

#### public static void
**shuffle**
([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<?\> list)

Randomly permutes the specified list using a default source of
randomness. All permutations occur with approximately equal
likelihood.

The hedge "approximately" is used in the foregoing description because
default source of randomness is only approximately an unbiased source
of independently chosen bits. If it were a perfect source of randomly
chosen bits, then the algorithm would choose permutations with perfect
uniformity.

This implementation traverses the list backwards, from the last
element up to the second, repeatedly swapping a randomly selected element
into the "current position". Elements are randomly selected from the
portion of the list that runs from the first element to the current
position, inclusive.

This method runs in linear time. If the specified list does not
implement the `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/RandomAccess.html` interface and is large, this
implementation dumps the specified list into an array before shuffling
it, and dumps the shuffled array back into the list. This avoids the
quadratic behavior that would result from shuffling a "sequential
access" list in place.

##### Parameters

| list | the list to be shuffled. |
|---|---|

##### Throws

| [UnsupportedOperationException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/UnsupportedOperationException.html) | if the specified list or its list-iterator does not support the set operation. |
|---|---|

#### public static [Set](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Set.html)\<T\>
**singleton**
(T o)

Returns an immutable set containing only the specified object.
The returned set is serializable.

##### Parameters

| o | the sole object to be stored in the returned set. |
|---|---|

##### Returns

- an immutable set containing only the specified object.

#### public static [List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<T\>
**singletonList**
(T o)

Returns an immutable list containing only the specified object.
The returned list is serializable.

##### Parameters

| o | the sole object to be stored in the returned list. |
|---|---|

##### Returns

- an immutable list containing only the specified object.

#### public static [Map](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html)\<K, V\>
**singletonMap**
(K key, V value)

Returns an immutable map, mapping only the specified key to the
specified value. The returned map is serializable.

##### Parameters

| key | the sole key to be stored in the returned map. |
| value | the value to which the returned map maps key. |
|---|---|

##### Returns

- an immutable map containing only the specified key-value mapping.

#### public static void
**sort**
([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<T\> list)

Sorts the specified list into ascending order, according to the
{@linkplain Comparable natural ordering} of its elements.
All elements in the list must implement the `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Comparable.html`
interface. Furthermore, all elements in the list must be
*mutually comparable* (that is, `e1.compareTo(e2)`
must not throw a `ClassCastException` for any elements
`e1` and `e2` in the list).

This sort is guaranteed to be *stable*: equal elements will
not be reordered as a result of the sort.

The specified list must be modifiable, but need not be resizable.

##### Parameters

| list | the list to be sorted. |
|---|---|

##### Throws

| [ClassCastException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ClassCastException.html) | if the list contains elements that are not *mutually comparable* (for example, strings and integers). |
| [UnsupportedOperationException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/UnsupportedOperationException.html) | if the specified list's list-iterator does not support the `set` operation. |
| [IllegalArgumentException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/IllegalArgumentException.html) | (optional) if the implementation detects that the natural ordering of the list elements is found to violate the `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Comparable.html` contract |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html#sort(java.util.Comparator<?%20super%20E>)`

#### public static void
**sort**
([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<T\> list, [Comparator](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Comparator.html)\<? super T\> c)

Sorts the specified list according to the order induced by the
specified comparator. All elements in the list must be *mutually comparable* using the specified comparator (that is,
`c.compare(e1, e2)` must not throw a `ClassCastException`
for any elements `e1` and `e2` in the list).

This sort is guaranteed to be *stable*: equal elements will
not be reordered as a result of the sort.

The specified list must be modifiable, but need not be resizable.

##### Parameters

| list | the list to be sorted. |
| c | the comparator to determine the order of the list. A `null` value indicates that the elements' *natural ordering* should be used. |
|---|---|

##### Throws

| [ClassCastException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ClassCastException.html) | if the list contains elements that are not *mutually comparable* using the specified comparator. |
| [UnsupportedOperationException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/UnsupportedOperationException.html) | if the specified list's list-iterator does not support the `set` operation. |
| [IllegalArgumentException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/IllegalArgumentException.html) | (optional) if the comparator is found to violate the `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Comparator.html` contract |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html#sort(java.util.Comparator<?%20super%20E>)`

#### public static void
**swap**
([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<?\> list, int i, int j)

Swaps the elements at the specified positions in the specified list.
(If the specified positions are equal, invoking this method leaves
the list unchanged.)

##### Parameters

| list | The list in which to swap elements. |
| i | the index of one element to be swapped. |
| j | the index of the other element to be swapped. |
|---|---|

##### Throws

| [IndexOutOfBoundsException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/IndexOutOfBoundsException.html) | if either i or j is out of range (i \< 0 \|\| i \>= list.size() \|\| j \< 0 \|\| j \>= list.size()). |
|---|---|

#### public static [Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<T\>
**synchronizedCollection**
([Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<T\> c)

Returns a synchronized (thread-safe) collection backed by the specified
collection. In order to guarantee serial access, it is critical that
**all** access to the backing collection is accomplished
through the returned collection.


It is imperative that the user manually synchronize on the returned
collection when traversing it via `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Iterator.html`, `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Spliterator.html`
or `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/stream/Stream.html`:

```
  Collection c = Collections.synchronizedCollection(myCollection);
     ...
  synchronized (c) {
      Iterator i = c.iterator(); // Must be in the synchronized block
      while (i.hasNext())
         foo(i.next());
  }
 
```
Failure to follow this advice may result in non-deterministic behavior.

The returned collection does *not* pass the `hashCode`
and `equals` operations through to the backing collection, but
relies on `Object`'s equals and hashCode methods. This is
necessary to preserve the contracts of these operations in the case
that the backing collection is a set or a list.


The returned collection will be serializable if the specified collection
is serializable.

##### Parameters

| c | the collection to be "wrapped" in a synchronized collection. |
|---|---|

##### Returns

- a synchronized view of the specified collection.

#### public static [List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<T\>
**synchronizedList**
([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<T\> list)

Returns a synchronized (thread-safe) list backed by the specified
list. In order to guarantee serial access, it is critical that
**all** access to the backing list is accomplished
through the returned list.


It is imperative that the user manually synchronize on the returned
list when iterating over it:

```
  List list = Collections.synchronizedList(new ArrayList());
      ...
  synchronized (list) {
      Iterator i = list.iterator(); // Must be in synchronized block
      while (i.hasNext())
          foo(i.next());
  }
 
```
Failure to follow this advice may result in non-deterministic behavior.

The returned list will be serializable if the specified list is
serializable.

##### Parameters

| list | the list to be "wrapped" in a synchronized list. |
|---|---|

##### Returns

- a synchronized view of the specified list.

#### public static [Map](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html)\<K, V\>
**synchronizedMap**
([Map](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html)\<K, V\> m)

Returns a synchronized (thread-safe) map backed by the specified
map. In order to guarantee serial access, it is critical that
**all** access to the backing map is accomplished
through the returned map.


It is imperative that the user manually synchronize on the returned
map when iterating over any of its collection views:

```
  Map m = Collections.synchronizedMap(new HashMap());
      ...
  Set s = m.keySet();  // Needn't be in synchronized block
      ...
  synchronized (m) {  // Synchronizing on m, not s!
      Iterator i = s.iterator(); // Must be in synchronized block
      while (i.hasNext())
          foo(i.next());
  }
 
```
Failure to follow this advice may result in non-deterministic behavior.

The returned map will be serializable if the specified map is
serializable.

##### Parameters

| m | the map to be "wrapped" in a synchronized map. |
|---|---|

##### Returns

- a synchronized view of the specified map.

#### public static [NavigableMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableMap.html)\<K, V\>
**synchronizedNavigableMap**
([NavigableMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableMap.html)\<K, V\> m)

Returns a synchronized (thread-safe) navigable map backed by the
specified navigable map. In order to guarantee serial access, it is
critical that **all** access to the backing navigable map is
accomplished through the returned navigable map (or its views).


It is imperative that the user manually synchronize on the returned
navigable map when iterating over any of its collection views, or the
collections views of any of its `subMap`, `headMap` or
`tailMap` views.

```
  NavigableMap m = Collections.synchronizedNavigableMap(new TreeMap());
      ...
  Set s = m.keySet();  // Needn't be in synchronized block
      ...
  synchronized (m) {  // Synchronizing on m, not s!
      Iterator i = s.iterator(); // Must be in synchronized block
      while (i.hasNext())
          foo(i.next());
  }
 
```
or:

```
  NavigableMap m = Collections.synchronizedNavigableMap(new TreeMap());
  NavigableMap m2 = m.subMap(foo, true, bar, false);
      ...
  Set s2 = m2.keySet();  // Needn't be in synchronized block
      ...
  synchronized (m) {  // Synchronizing on m, not m2 or s2!
      Iterator i = s.iterator(); // Must be in synchronized block
      while (i.hasNext())
          foo(i.next());
  }
 
```
Failure to follow this advice may result in non-deterministic behavior.

The returned navigable map will be serializable if the specified
navigable map is serializable.

##### Parameters

| m | the navigable map to be "wrapped" in a synchronized navigable map |
|---|---|

##### Returns

- a synchronized view of the specified navigable map.

#### public static [NavigableSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableSet.html)\<T\>
**synchronizedNavigableSet**
([NavigableSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableSet.html)\<T\> s)

Returns a synchronized (thread-safe) navigable set backed by the
specified navigable set. In order to guarantee serial access, it is
critical that **all** access to the backing navigable set is
accomplished through the returned navigable set (or its views).


It is imperative that the user manually synchronize on the returned
navigable set when iterating over it or any of its `subSet`,
`headSet`, or `tailSet` views.

```
  NavigableSet s = Collections.synchronizedNavigableSet(new TreeSet());
      ...
  synchronized (s) {
      Iterator i = s.iterator(); // Must be in the synchronized block
      while (i.hasNext())
          foo(i.next());
  }
 
```
or:

```
  NavigableSet s = Collections.synchronizedNavigableSet(new TreeSet());
  NavigableSet s2 = s.headSet(foo, true);
      ...
  synchronized (s) {  // Note: s, not s2!!!
      Iterator i = s2.iterator(); // Must be in the synchronized block
      while (i.hasNext())
          foo(i.next());
  }
 
```
Failure to follow this advice may result in non-deterministic behavior.

The returned navigable set will be serializable if the specified
navigable set is serializable.

##### Parameters

| s | the navigable set to be "wrapped" in a synchronized navigable set |
|---|---|

##### Returns

- a synchronized view of the specified navigable set

#### public static [Set](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Set.html)\<T\>
**synchronizedSet**
([Set](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Set.html)\<T\> s)

Returns a synchronized (thread-safe) set backed by the specified
set. In order to guarantee serial access, it is critical that
**all** access to the backing set is accomplished
through the returned set.


It is imperative that the user manually synchronize on the returned
set when iterating over it:

```
  Set s = Collections.synchronizedSet(new HashSet());
      ...
  synchronized (s) {
      Iterator i = s.iterator(); // Must be in the synchronized block
      while (i.hasNext())
          foo(i.next());
  }
 
```
Failure to follow this advice may result in non-deterministic behavior.

The returned set will be serializable if the specified set is
serializable.

##### Parameters

| s | the set to be "wrapped" in a synchronized set. |
|---|---|

##### Returns

- a synchronized view of the specified set.

#### public static [SortedMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedMap.html)\<K, V\>
**synchronizedSortedMap**
([SortedMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedMap.html)\<K, V\> m)

Returns a synchronized (thread-safe) sorted map backed by the specified
sorted map. In order to guarantee serial access, it is critical that
**all** access to the backing sorted map is accomplished
through the returned sorted map (or its views).


It is imperative that the user manually synchronize on the returned
sorted map when iterating over any of its collection views, or the
collections views of any of its subMap, headMap or
tailMap views.

```
  SortedMap m = Collections.synchronizedSortedMap(new TreeMap());
      ...
  Set s = m.keySet();  // Needn't be in synchronized block
      ...
  synchronized (m) {  // Synchronizing on m, not s!
      Iterator i = s.iterator(); // Must be in synchronized block
      while (i.hasNext())
          foo(i.next());
  }
 
```
or:

```
  SortedMap m = Collections.synchronizedSortedMap(new TreeMap());
  SortedMap m2 = m.subMap(foo, bar);
      ...
  Set s2 = m2.keySet();  // Needn't be in synchronized block
      ...
  synchronized (m) {  // Synchronizing on m, not m2 or s2!
      Iterator i = s.iterator(); // Must be in synchronized block
      while (i.hasNext())
          foo(i.next());
  }
 
```
Failure to follow this advice may result in non-deterministic behavior.

The returned sorted map will be serializable if the specified
sorted map is serializable.

##### Parameters

| m | the sorted map to be "wrapped" in a synchronized sorted map. |
|---|---|

##### Returns

- a synchronized view of the specified sorted map.

#### public static [SortedSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedSet.html)\<T\>
**synchronizedSortedSet**
([SortedSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedSet.html)\<T\> s)

Returns a synchronized (thread-safe) sorted set backed by the specified
sorted set. In order to guarantee serial access, it is critical that
**all** access to the backing sorted set is accomplished
through the returned sorted set (or its views).


It is imperative that the user manually synchronize on the returned
sorted set when iterating over it or any of its subSet,
headSet, or tailSet views.

```
  SortedSet s = Collections.synchronizedSortedSet(new TreeSet());
      ...
  synchronized (s) {
      Iterator i = s.iterator(); // Must be in the synchronized block
      while (i.hasNext())
          foo(i.next());
  }
 
```
or:

```
  SortedSet s = Collections.synchronizedSortedSet(new TreeSet());
  SortedSet s2 = s.headSet(foo);
      ...
  synchronized (s) {  // Note: s, not s2!!!
      Iterator i = s2.iterator(); // Must be in the synchronized block
      while (i.hasNext())
          foo(i.next());
  }
 
```
Failure to follow this advice may result in non-deterministic behavior.

The returned sorted set will be serializable if the specified
sorted set is serializable.

##### Parameters

| s | the sorted set to be "wrapped" in a synchronized sorted set. |
|---|---|

##### Returns

- a synchronized view of the specified sorted set.

#### public static [Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<T\>
**unmodifiableCollection**
([Collection](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Collection.html)\<? extends T\> c)

Returns an unmodifiable view of the specified collection. This method
allows modules to provide users with "read-only" access to internal
collections. Query operations on the returned collection "read through"
to the specified collection, and attempts to modify the returned
collection, whether direct or via its iterator, result in an
UnsupportedOperationException.


The returned collection does *not* pass the hashCode and equals
operations through to the backing collection, but relies on
Object's equals and hashCode methods. This
is necessary to preserve the contracts of these operations in the case
that the backing collection is a set or a list.


The returned collection will be serializable if the specified collection
is serializable.

##### Parameters

| c | the collection for which an unmodifiable view is to be returned. |
|---|---|

##### Returns

- an unmodifiable view of the specified collection.

#### public static [List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<T\>
**unmodifiableList**
([List](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/List.html)\<? extends T\> list)

Returns an unmodifiable view of the specified list. This method allows
modules to provide users with "read-only" access to internal
lists. Query operations on the returned list "read through" to the
specified list, and attempts to modify the returned list, whether
direct or via its iterator, result in an
UnsupportedOperationException.


The returned list will be serializable if the specified list
is serializable. Similarly, the returned list will implement
`https://developers.google.com/j2objc/javadoc/jre/reference/java/util/RandomAccess.html` if the specified list does.

##### Parameters

| list | the list for which an unmodifiable view is to be returned. |
|---|---|

##### Returns

- an unmodifiable view of the specified list.

#### public static [Map](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html)\<K, V\>
**unmodifiableMap**
([Map](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Map.html)\<? extends K, ? extends V\> m)

Returns an unmodifiable view of the specified map. This method
allows modules to provide users with "read-only" access to internal
maps. Query operations on the returned map "read through"
to the specified map, and attempts to modify the returned
map, whether direct or via its collection views, result in an
UnsupportedOperationException.


The returned map will be serializable if the specified map
is serializable.

##### Parameters

| m | the map for which an unmodifiable view is to be returned. |
|---|---|

##### Returns

- an unmodifiable view of the specified map.

#### public static [NavigableMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableMap.html)\<K, V\>
**unmodifiableNavigableMap**
([NavigableMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableMap.html)\<K, ? extends V\> m)

Returns an unmodifiable view of the specified navigable map. This method
allows modules to provide users with "read-only" access to internal
navigable maps. Query operations on the returned navigable map "read
through" to the specified navigable map. Attempts to modify the returned
navigable map, whether direct, via its collection views, or via its
`subMap`, `headMap`, or `tailMap` views, result in
an `UnsupportedOperationException`.


The returned navigable map will be serializable if the specified
navigable map is serializable.

##### Parameters

| m | the navigable map for which an unmodifiable view is to be returned |
|---|---|

##### Returns

- an unmodifiable view of the specified navigable map

#### public static [NavigableSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableSet.html)\<T\>
**unmodifiableNavigableSet**
([NavigableSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/NavigableSet.html)\<T\> s)

Returns an unmodifiable view of the specified navigable set. This method
allows modules to provide users with "read-only" access to internal
navigable sets. Query operations on the returned navigable set "read
through" to the specified navigable set. Attempts to modify the returned
navigable set, whether direct, via its iterator, or via its
`subSet`, `headSet`, or `tailSet` views, result in
an `UnsupportedOperationException`.


The returned navigable set will be serializable if the specified
navigable set is serializable.

##### Parameters

| s | the navigable set for which an unmodifiable view is to be returned |
|---|---|

##### Returns

- an unmodifiable view of the specified navigable set

#### public static [Set](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Set.html)\<T\>
**unmodifiableSet**
([Set](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/Set.html)\<? extends T\> s)

Returns an unmodifiable view of the specified set. This method allows
modules to provide users with "read-only" access to internal sets.
Query operations on the returned set "read through" to the specified
set, and attempts to modify the returned set, whether direct or via its
iterator, result in an UnsupportedOperationException.


The returned set will be serializable if the specified set
is serializable.

##### Parameters

| s | the set for which an unmodifiable view is to be returned. |
|---|---|

##### Returns

- an unmodifiable view of the specified set.

#### public static [SortedMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedMap.html)\<K, V\>
**unmodifiableSortedMap**
([SortedMap](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedMap.html)\<K, ? extends V\> m)

Returns an unmodifiable view of the specified sorted map. This method
allows modules to provide users with "read-only" access to internal
sorted maps. Query operations on the returned sorted map "read through"
to the specified sorted map. Attempts to modify the returned
sorted map, whether direct, via its collection views, or via its
subMap, headMap, or tailMap views, result in
an UnsupportedOperationException.


The returned sorted map will be serializable if the specified sorted map
is serializable.

##### Parameters

| m | the sorted map for which an unmodifiable view is to be returned. |
|---|---|

##### Returns

- an unmodifiable view of the specified sorted map.

#### public static [SortedSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedSet.html)\<T\>
**unmodifiableSortedSet**
([SortedSet](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/SortedSet.html)\<T\> s)

Returns an unmodifiable view of the specified sorted set. This method
allows modules to provide users with "read-only" access to internal
sorted sets. Query operations on the returned sorted set "read
through" to the specified sorted set. Attempts to modify the returned
sorted set, whether direct, via its iterator, or via its
subSet, headSet, or tailSet views, result in
an UnsupportedOperationException.


The returned sorted set will be serializable if the specified sorted set
is serializable.

##### Parameters

| s | the sorted set for which an unmodifiable view is to be returned. |
|---|---|

##### Returns

- an unmodifiable view of the specified sorted set.