TreeMap

AI-generated Key Takeaways

• TreeMap is a Java collection that stores key-value pairs in sorted order, using either natural ordering or a custom Comparator.

• It provides efficient retrieval, insertion, and deletion operations with logarithmic time complexity (O(log n)).

• TreeMap offers navigation methods like firstKey, lastKey, higherKey, and lowerKey for traversing the sorted entries.

• It supports views of portions of the map through methods like headMap, tailMap, and subMap.

• TreeMap is not thread-safe, requiring external synchronization for concurrent access to avoid issues.

public class TreeMap extends AbstractMap<K, V>
implements NavigableMap<K, V> Cloneable Serializable

A Red-Black tree based NavigableMap implementation. The map is sorted according to the {@linkplain Comparable natural ordering} of its keys, or by a Comparator provided at map creation time, depending on which constructor is used.

This implementation provides guaranteed log(n) time cost for the containsKey, get, put and remove operations. Algorithms are adaptations of those in Cormen, Leiserson, and Rivest's Introduction to Algorithms.

Note that the ordering maintained by a tree map, like any sorted map, and whether or not an explicit comparator is provided, must be consistent with equals if this sorted map is to correctly implement the Map interface. (See Comparable or Comparator for a precise definition of consistent with equals.) This is so because the Map interface is defined in terms of the equals operation, but a sorted map performs all key comparisons using its compareTo (or compare) method, so two keys that are deemed equal by this method are, from the standpoint of the sorted map, equal. The behavior of a sorted map is well-defined even if its ordering is inconsistent with equals; it just fails to obey the general contract of the Map interface.

Note that this implementation is not synchronized. If multiple threads access a map concurrently, and at least one of the threads modifies the map structurally, it must be synchronized externally. (A structural modification is any operation that adds or deletes one or more mappings; merely changing the value associated with an existing key is not a structural modification.) This is typically accomplished by synchronizing on some object that naturally encapsulates the map. If no such object exists, the map should be "wrapped" using the Collections.synchronizedSortedMap method. This is best done at creation time, to prevent accidental unsynchronized access to the map:

   SortedMap m = Collections.synchronizedSortedMap(new TreeMap(...));

The iterators returned by the iterator method of the collections returned by all of this class's "collection view methods" are fail-fast: if the map is structurally modified at any time after the iterator is created, in any way except through the iterator's own remove method, the iterator will throw a ConcurrentModificationException. Thus, in the face of concurrent modification, the iterator fails quickly and cleanly, rather than risking arbitrary, non-deterministic behavior at an undetermined time in the future.

Note that the fail-fast behavior of an iterator cannot be guaranteed as it is, generally speaking, impossible to make any hard guarantees in the presence of unsynchronized concurrent modification. Fail-fast iterators throw ConcurrentModificationException on a best-effort basis. Therefore, it would be wrong to write a program that depended on this exception for its correctness: the fail-fast behavior of iterators should be used only to detect bugs.

All Map.Entry pairs returned by methods in this class and its views represent snapshots of mappings at the time they were produced. They do not support the Entry.setValue method. (Note however that it is possible to change mappings in the associated map using put.)

This class is a member of the Java Collections Framework.

See Also

• Map
• HashMap
• Hashtable
• Comparable
• Comparator
• Collection

Public Constructor Summary

	TreeMap() Constructs a new, empty tree map, using the natural ordering of its keys.
	TreeMap(Comparator<? super K> comparator) Constructs a new, empty tree map, ordered according to the given comparator.
	TreeMap(Map<? extends K, ? extends V> m) Constructs a new tree map containing the same mappings as the given map, ordered according to the natural ordering of its keys.
	TreeMap(SortedMap<K, ? extends V> m) Constructs a new tree map containing the same mappings and using the same ordering as the specified sorted map.

Public Method Summary

Entry<K, V>	ceilingEntry(K key) Returns a key-value mapping associated with the least key greater than or equal to the given key, or null if there is no such key.
K	ceilingKey(K key) Returns the least key greater than or equal to the given key, or null if there is no such key.
void	clear() Removes all of the mappings from this map.
Object	clone() Returns a shallow copy of this TreeMap instance.
Comparator<? super K>	comparator() Returns the comparator used to order the keys in this map, or null if this map uses the {@linkplain Comparable natural ordering} of its keys.
boolean	containsKey(Object key) Returns true if this map contains a mapping for the specified key.
boolean	containsValue(Object value) Returns true if this map maps one or more keys to the specified value.
NavigableSet<K>	descendingKeySet() Returns a reverse order NavigableSet view of the keys contained in this map.
NavigableMap<K, V>	descendingMap() Returns a reverse order view of the mappings contained in this map.
Set<Entry<K, V>>	entrySet() Returns a Set view of the mappings contained in this map.
Entry<K, V>	firstEntry() Returns a key-value mapping associated with the least key in this map, or null if the map is empty.
K	firstKey() Returns the first (lowest) key currently in this map.
Entry<K, V>	floorEntry(K key) Returns a key-value mapping associated with the greatest key less than or equal to the given key, or null if there is no such key.
K	floorKey(K key) Returns the greatest key less than or equal to the given key, or null if there is no such key.
void	forEach(BiConsumer<? super K, ? super V> action) Performs the given action for each entry in this map until all entries have been processed or the action throws an exception.
V	get(Object key) Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.
SortedMap<K, V>	headMap(K toKey) Returns a view of the portion of this map whose keys are strictly less than toKey. Equivalent to headMap(toKey, false).
NavigableMap<K, V>	headMap(K toKey, boolean inclusive) Returns a view of the portion of this map whose keys are less than (or equal to, if inclusive is true) toKey.
Entry<K, V>	higherEntry(K key) Returns a key-value mapping associated with the least key strictly greater than the given key, or null if there is no such key.
K	higherKey(K key) Returns the least key strictly greater than the given key, or null if there is no such key.
Set<K>	keySet() Returns a Set view of the keys contained in this map.
Entry<K, V>	lastEntry() Returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.
K	lastKey() Returns the last (highest) key currently in this map.
Entry<K, V>	lowerEntry(K key) Returns a key-value mapping associated with the greatest key strictly less than the given key, or null if there is no such key.
K	lowerKey(K key) Returns the greatest key strictly less than the given key, or null if there is no such key.
NavigableSet<K>	navigableKeySet() Returns a NavigableSet view of the keys contained in this map.
Entry<K, V>	pollFirstEntry() Removes and returns a key-value mapping associated with the least key in this map, or null if the map is empty.
Entry<K, V>	pollLastEntry() Removes and returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.
V	put(K key, V value) Associates the specified value with the specified key in this map.
void	putAll(Map<? extends K, ? extends V> map) Copies all of the mappings from the specified map to this map.
V	remove(Object key) Removes the mapping for this key from this TreeMap if present.
void	replaceAll(BiFunction<? super K, ? super V, ? extends V> function) Replaces each entry's value with the result of invoking the given function on that entry until all entries have been processed or the function throws an exception.
int	size() Returns the number of key-value mappings in this map.
SortedMap<K, V>	subMap(K fromKey, K toKey) Returns a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive. Equivalent to subMap(fromKey, true, toKey, false).
NavigableMap<K, V>	subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) Returns a view of the portion of this map whose keys range from fromKey to toKey.
NavigableMap<K, V>	tailMap(K fromKey, boolean inclusive) Returns a view of the portion of this map whose keys are greater than (or equal to, if inclusive is true) fromKey.
SortedMap<K, V>	tailMap(K fromKey) Returns a view of the portion of this map whose keys are greater than or equal to fromKey. Equivalent to tailMap(fromKey, true).
Collection<V>	values() Returns a Collection view of the values contained in this map.

Inherited Method Summary

From class java.util.AbstractMap

void	clear() Removes all of the mappings from this map (optional operation).
Object	clone() Returns a shallow copy of this AbstractMap instance: the keys and values themselves are not cloned.
boolean	containsKey(Object key) Returns true if this map contains a mapping for the specified key.
boolean	containsValue(Object value) Returns true if this map maps one or more keys to the specified value.
abstract Set<Entry<K, V>>	entrySet() Returns a Set view of the mappings contained in this map.
boolean	equals(Object o) Compares the specified object with this map for equality.
V	get(Object key) Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.
int	hashCode() Returns the hash code value for this map.
boolean	isEmpty() Returns true if this map contains no key-value mappings.
Set<K>	keySet() Returns a Set view of the keys contained in this map.
V	put(K key, V value) Associates the specified value with the specified key in this map (optional operation).
void	putAll(Map<? extends K, ? extends V> m) Copies all of the mappings from the specified map to this map (optional operation).
V	remove(Object key) Removes the mapping for a key from this map if it is present (optional operation).
int	size() Returns the number of key-value mappings in this map.
String	toString() Returns a string representation of this map.
Collection<V>	values() Returns a Collection view of the values contained in this map.

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	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() 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	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(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(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() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

From interface java.util.Map

abstract void	clear() Removes all of the mappings from this map (optional operation).
V	compute(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) Attempts to compute a mapping for the specified key and its current mapped value (or null if there is no current mapping).
V	computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction) If the specified key is not already associated with a value (or is mapped to null), attempts to compute its value using the given mapping function and enters it into this map unless null.
V	computeIfPresent(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) If the value for the specified key is present and non-null, attempts to compute a new mapping given the key and its current mapped value.
abstract boolean	containsKey(Object key) Returns true if this map contains a mapping for the specified key.
abstract boolean	containsValue(Object value) Returns true if this map maps one or more keys to the specified value.
abstract Set<Entry<K, V>>	entrySet() Returns a Set view of the mappings contained in this map.
abstract boolean	equals(Object o) Compares the specified object with this map for equality.
void	forEach(BiConsumer<? super K, ? super V> action) Performs the given action for each entry in this map until all entries have been processed or the action throws an exception.
abstract V	get(Object key) Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.
V	getOrDefault(Object key, V defaultValue) Returns the value to which the specified key is mapped, or defaultValue if this map contains no mapping for the key.
abstract int	hashCode() Returns the hash code value for this map.
abstract boolean	isEmpty() Returns true if this map contains no key-value mappings.
abstract Set<K>	keySet() Returns a Set view of the keys contained in this map.
V	merge(K key, V value, BiFunction<? super V, ? super V, ? extends V> remappingFunction) If the specified key is not already associated with a value or is associated with null, associates it with the given non-null value.
abstract V	put(K key, V value) Associates the specified value with the specified key in this map (optional operation).
abstract void	putAll(Map<? extends K, ? extends V> m) Copies all of the mappings from the specified map to this map (optional operation).
V	putIfAbsent(K key, V value) If the specified key is not already associated with a value (or is mapped to null) associates it with the given value and returns null, else returns the current value.
boolean	remove(Object key, Object value) Removes the entry for the specified key only if it is currently mapped to the specified value.
abstract V	remove(Object key) Removes the mapping for a key from this map if it is present (optional operation).
boolean	replace(K key, V oldValue, V newValue) Replaces the entry for the specified key only if currently mapped to the specified value.
V	replace(K key, V value) Replaces the entry for the specified key only if it is currently mapped to some value.
void	replaceAll(BiFunction<? super K, ? super V, ? extends V> function) Replaces each entry's value with the result of invoking the given function on that entry until all entries have been processed or the function throws an exception.
abstract int	size() Returns the number of key-value mappings in this map.
abstract Collection<V>	values() Returns a Collection view of the values contained in this map.

From interface java.util.NavigableMap

abstract Entry<K, V>	ceilingEntry(K key) Returns a key-value mapping associated with the least key greater than or equal to the given key, or null if there is no such key.
abstract K	ceilingKey(K key) Returns the least key greater than or equal to the given key, or null if there is no such key.
abstract NavigableSet<K>	descendingKeySet() Returns a reverse order NavigableSet view of the keys contained in this map.
abstract NavigableMap<K, V>	descendingMap() Returns a reverse order view of the mappings contained in this map.
abstract Entry<K, V>	firstEntry() Returns a key-value mapping associated with the least key in this map, or null if the map is empty.
abstract Entry<K, V>	floorEntry(K key) Returns a key-value mapping associated with the greatest key less than or equal to the given key, or null if there is no such key.
abstract K	floorKey(K key) Returns the greatest key less than or equal to the given key, or null if there is no such key.
abstract SortedMap<K, V>	headMap(K toKey) Returns a view of the portion of this map whose keys are strictly less than toKey. Equivalent to headMap(toKey, false).
abstract NavigableMap<K, V>	headMap(K toKey, boolean inclusive) Returns a view of the portion of this map whose keys are less than (or equal to, if inclusive is true) toKey.
abstract Entry<K, V>	higherEntry(K key) Returns a key-value mapping associated with the least key strictly greater than the given key, or null if there is no such key.
abstract K	higherKey(K key) Returns the least key strictly greater than the given key, or null if there is no such key.
abstract Entry<K, V>	lastEntry() Returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.
abstract Entry<K, V>	lowerEntry(K key) Returns a key-value mapping associated with the greatest key strictly less than the given key, or null if there is no such key.
abstract K	lowerKey(K key) Returns the greatest key strictly less than the given key, or null if there is no such key.
abstract NavigableSet<K>	navigableKeySet() Returns a NavigableSet view of the keys contained in this map.
abstract Entry<K, V>	pollFirstEntry() Removes and returns a key-value mapping associated with the least key in this map, or null if the map is empty.
abstract Entry<K, V>	pollLastEntry() Removes and returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.
abstract SortedMap<K, V>	subMap(K fromKey, K toKey) Returns a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive. Equivalent to subMap(fromKey, true, toKey, false).
abstract NavigableMap<K, V>	subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) Returns a view of the portion of this map whose keys range from fromKey to toKey.
abstract NavigableMap<K, V>	tailMap(K fromKey, boolean inclusive) Returns a view of the portion of this map whose keys are greater than (or equal to, if inclusive is true) fromKey.
abstract SortedMap<K, V>	tailMap(K fromKey) Returns a view of the portion of this map whose keys are greater than or equal to fromKey. Equivalent to tailMap(fromKey, true).

From interface java.util.SortedMap

abstract Comparator<? super K>	comparator() Returns the comparator used to order the keys in this map, or null if this map uses the {@linkplain Comparable natural ordering} of its keys.
abstract Set<Entry<K, V>>	entrySet() Returns a Set view of the mappings contained in this map.
abstract K	firstKey() Returns the first (lowest) key currently in this map.
abstract SortedMap<K, V>	headMap(K toKey) Returns a view of the portion of this map whose keys are strictly less than toKey.
abstract Set<K>	keySet() Returns a Set view of the keys contained in this map.
abstract K	lastKey() Returns the last (highest) key currently in this map.
abstract SortedMap<K, V>	subMap(K fromKey, K toKey) Returns a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive.
abstract SortedMap<K, V>	tailMap(K fromKey) Returns a view of the portion of this map whose keys are greater than or equal to fromKey.
abstract Collection<V>	values() Returns a Collection view of the values contained in this map.

Public Constructors

public TreeMap ()

Constructs a new, empty tree map, using the natural ordering of its keys. All keys inserted into the map must implement the Comparable interface. Furthermore, all such keys must be mutually comparable: k1.compareTo(k2) must not throw a ClassCastException for any keys k1 and k2 in the map. If the user attempts to put a key into the map that violates this constraint (for example, the user attempts to put a string key into a map whose keys are integers), the put(Object key, Object value) call will throw a ClassCastException.

public TreeMap (Comparator<? super K> comparator)

Constructs a new, empty tree map, ordered according to the given comparator. All keys inserted into the map must be mutually comparable by the given comparator: comparator.compare(k1, k2) must not throw a ClassCastException for any keys k1 and k2 in the map. If the user attempts to put a key into the map that violates this constraint, the put(Object key, Object value) call will throw a ClassCastException.

Parameters

comparator	the comparator that will be used to order this map. If null, the {@linkplain Comparable natural ordering} of the keys will be used.

public TreeMap (Map<? extends K, ? extends V> m)

Constructs a new tree map containing the same mappings as the given map, ordered according to the natural ordering of its keys. All keys inserted into the new map must implement the Comparable interface. Furthermore, all such keys must be mutually comparable: k1.compareTo(k2) must not throw a ClassCastException for any keys k1 and k2 in the map. This method runs in n*log(n) time.

Parameters

m	the map whose mappings are to be placed in this map

Throws

ClassCastException	if the keys in m are not Comparable, or are not mutually comparable
NullPointerException	if the specified map is null

public TreeMap (SortedMap<K, ? extends V> m)

Constructs a new tree map containing the same mappings and using the same ordering as the specified sorted map. This method runs in linear time.

Parameters

m	the sorted map whose mappings are to be placed in this map, and whose comparator is to be used to sort this map

Throws

NullPointerException	if the specified map is null

Public Methods

public Entry<K, V> ceilingEntry (K key)

Returns a key-value mapping associated with the least key greater than or equal to the given key, or null if there is no such key.

Parameters

key	the key

Returns

• an entry with the least key greater than or equal to key, or null if there is no such key

Throws

ClassCastException
NullPointerException	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

public K ceilingKey (K key)

Returns the least key greater than or equal to the given key, or null if there is no such key.

Parameters

key	the key

Returns

• the least key greater than or equal to key, or null if there is no such key

Throws

ClassCastException
NullPointerException	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

public void clear ()

Removes all of the mappings from this map. The map will be empty after this call returns.

public Object clone ()

Returns a shallow copy of this TreeMap instance. (The keys and values themselves are not cloned.)

Returns

• a shallow copy of this map

public Comparator<? super K> comparator ()

Returns the comparator used to order the keys in this map, or null if this map uses the {@linkplain Comparable natural ordering} of its keys.

Returns

• the comparator used to order the keys in this map, or null if this map uses the natural ordering of its keys

public boolean containsKey (Object key)

Returns true if this map contains a mapping for the specified key.

Parameters

key	key whose presence in this map is to be tested

Returns

• true if this map contains a mapping for the specified key

Throws

ClassCastException	if the specified key cannot be compared with the keys currently in the map
NullPointerException	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

public boolean containsValue (Object value)

Returns true if this map maps one or more keys to the specified value. More formally, returns true if and only if this map contains at least one mapping to a value v such that (value==null ? v==null : value.equals(v)). This operation will probably require time linear in the map size for most implementations.

Parameters

value	value whose presence in this map is to be tested

Returns

• true if a mapping to value exists; false otherwise

public NavigableSet<K> descendingKeySet ()

Returns a reverse order NavigableSet view of the keys contained in this map. The set's iterator returns the keys in descending order. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress (except through the iterator's own remove operation), the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Set.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.

Returns

• a reverse order navigable set view of the keys in this map

public NavigableMap<K, V> descendingMap ()

Returns a reverse order view of the mappings contained in this map. The descending map is backed by this map, so changes to the map are reflected in the descending map, and vice-versa. If either map is modified while an iteration over a collection view of either map is in progress (except through the iterator's own remove operation), the results of the iteration are undefined.

The returned map has an ordering equivalent to Collections.reverseOrder(comparator()). The expression m.descendingMap().descendingMap() returns a view of m essentially equivalent to m.

Returns

• a reverse order view of this map

public Set<Entry<K, V>> entrySet ()

Returns a Set view of the mappings contained in this map.

The set's iterator returns the entries in ascending key order. The sets's spliterator is late-binding, fail-fast, and additionally reports Spliterator.SORTED and Spliterator.ORDERED with an encounter order that is ascending key order.

The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress (except through the iterator's own remove operation, or through the setValue operation on a map entry returned by the iterator) the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Set.remove, removeAll, retainAll and clear operations. It does not support the add or addAll operations.

Returns

• a set view of the mappings contained in this map

public Entry<K, V> firstEntry ()

Returns a key-value mapping associated with the least key in this map, or null if the map is empty.

Returns

• an entry with the least key, or null if this map is empty

public K firstKey ()

Returns the first (lowest) key currently in this map.

Returns

• the first (lowest) key currently in this map

Throws

NoSuchElementException

public Entry<K, V> floorEntry (K key)

Returns a key-value mapping associated with the greatest key less than or equal to the given key, or null if there is no such key.

Parameters

key	the key

Returns

• an entry with the greatest key less than or equal to key, or null if there is no such key

Throws

ClassCastException
NullPointerException	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

public K floorKey (K key)

Returns the greatest key less than or equal to the given key, or null if there is no such key.

Parameters

key	the key

Returns

• the greatest key less than or equal to key, or null if there is no such key

Throws

ClassCastException
NullPointerException	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

public void forEach (BiConsumer<? super K, ? super V> action)

Performs the given action for each entry in this map until all entries have been processed or the action throws an exception. Unless otherwise specified by the implementing class, actions are performed in the order of entry set iteration (if an iteration order is specified.) Exceptions thrown by the action are relayed to the caller.

Parameters

action	The action to be performed for each entry

public V get (Object key)

Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.

More formally, if this map contains a mapping from a key k to a value v such that key compares equal to k according to the map's ordering, then this method returns v; otherwise it returns null. (There can be at most one such mapping.)

A return value of null does not necessarily indicate that the map contains no mapping for the key; it's also possible that the map explicitly maps the key to null. The containsKey operation may be used to distinguish these two cases.

Parameters

key	the key whose associated value is to be returned

Returns

• the value to which the specified key is mapped, or null if this map contains no mapping for the key

Throws

ClassCastException	if the specified key cannot be compared with the keys currently in the map
NullPointerException	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

public SortedMap<K, V> headMap (K toKey)

Returns a view of the portion of this map whose keys are strictly less than toKey. The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports.

The returned map will throw an IllegalArgumentException on an attempt to insert a key outside its range.

Equivalent to headMap(toKey, false).

Parameters

toKey	high endpoint (exclusive) of the keys in the returned map

Returns

• a view of the portion of this map whose keys are strictly less than toKey

Throws

ClassCastException
NullPointerException	if toKey is null and this map uses natural ordering, or its comparator does not permit null keys
IllegalArgumentException

public NavigableMap<K, V> headMap (K toKey, boolean inclusive)

Returns a view of the portion of this map whose keys are less than (or equal to, if inclusive is true) toKey. The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports.

The returned map will throw an IllegalArgumentException on an attempt to insert a key outside its range.

Parameters

toKey	high endpoint of the keys in the returned map
inclusive	true if the high endpoint is to be included in the returned view

Returns

• a view of the portion of this map whose keys are less than (or equal to, if inclusive is true) toKey

Throws

ClassCastException
NullPointerException	if toKey is null and this map uses natural ordering, or its comparator does not permit null keys
IllegalArgumentException

public Entry<K, V> higherEntry (K key)

Returns a key-value mapping associated with the least key strictly greater than the given key, or null if there is no such key.

Parameters

key	the key

Returns

• an entry with the least key greater than key, or null if there is no such key

Throws

ClassCastException
NullPointerException	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

public K higherKey (K key)

Returns the least key strictly greater than the given key, or null if there is no such key.

Parameters

key	the key

Returns

• the least key greater than key, or null if there is no such key

Throws

ClassCastException
NullPointerException	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

public Set<K> keySet ()

Returns a Set view of the keys contained in this map.

The set's iterator returns the keys in ascending order. The set's spliterator is late-binding, fail-fast, and additionally reports Spliterator.SORTED and Spliterator.ORDERED with an encounter order that is ascending key order. The spliterator's comparator (see Spliterator.getComparator()) is null if the tree map's comparator (see comparator()) is null. Otherwise, the spliterator's comparator is the same as or imposes the same total ordering as the tree map's comparator.

The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress (except through the iterator's own remove operation), the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Set.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.

Returns

• a set view of the keys contained in this map

public Entry<K, V> lastEntry ()

Returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.

Returns

• an entry with the greatest key, or null if this map is empty

public K lastKey ()

Returns the last (highest) key currently in this map.

Returns

• the last (highest) key currently in this map

Throws

NoSuchElementException

public Entry<K, V> lowerEntry (K key)

Returns a key-value mapping associated with the greatest key strictly less than the given key, or null if there is no such key.

Parameters

key	the key

Returns

• an entry with the greatest key less than key, or null if there is no such key

Throws

ClassCastException
NullPointerException	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

public K lowerKey (K key)

Returns the greatest key strictly less than the given key, or null if there is no such key.

Parameters

key	the key

Returns

• the greatest key less than key, or null if there is no such key

Throws

ClassCastException
NullPointerException	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

public NavigableSet<K> navigableKeySet ()

Returns a NavigableSet view of the keys contained in this map. The set's iterator returns the keys in ascending order. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress (except through the iterator's own remove operation), the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Set.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.

Returns

• a navigable set view of the keys in this map

public Entry<K, V> pollFirstEntry ()

Removes and returns a key-value mapping associated with the least key in this map, or null if the map is empty.

Returns

• the removed first entry of this map, or null if this map is empty

public Entry<K, V> pollLastEntry ()

Removes and returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.

Returns

• the removed last entry of this map, or null if this map is empty

public V put (K key, V value)

Associates the specified value with the specified key in this map. If the map previously contained a mapping for the key, the old value is replaced.

Parameters

key	key with which the specified value is to be associated
value	value to be associated with the specified key

Returns

• the previous value associated with key, or null if there was no mapping for key. (A null return can also indicate that the map previously associated null with key.)

Throws

ClassCastException	if the specified key cannot be compared with the keys currently in the map
NullPointerException	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

public void putAll (Map<? extends K, ? extends V> map)

Copies all of the mappings from the specified map to this map. These mappings replace any mappings that this map had for any of the keys currently in the specified map.

Parameters

map	mappings to be stored in this map

Throws

ClassCastException	if the class of a key or value in the specified map prevents it from being stored in this map
NullPointerException	if the specified map is null or the specified map contains a null key and this map does not permit null keys

public V remove (Object key)

Removes the mapping for this key from this TreeMap if present.

Parameters

key	key for which mapping should be removed

Returns

• the previous value associated with key, or null if there was no mapping for key. (A null return can also indicate that the map previously associated null with key.)

Throws

ClassCastException	if the specified key cannot be compared with the keys currently in the map
NullPointerException	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

public void replaceAll (BiFunction<? super K, ? super V, ? extends V> function)

Replaces each entry's value with the result of invoking the given function on that entry until all entries have been processed or the function throws an exception. Exceptions thrown by the function are relayed to the caller.

Parameters

function	the function to apply to each entry

public int size ()

Returns the number of key-value mappings in this map.

Returns

• the number of key-value mappings in this map

public SortedMap<K, V> subMap (K fromKey, K toKey)

Returns a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive. (If fromKey and toKey are equal, the returned map is empty.) The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports.

The returned map will throw an IllegalArgumentException on an attempt to insert a key outside its range.

Equivalent to subMap(fromKey, true, toKey, false).

Parameters

fromKey	low endpoint (inclusive) of the keys in the returned map
toKey	high endpoint (exclusive) of the keys in the returned map

Returns

• a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive

Throws

ClassCastException
NullPointerException	if fromKey or toKey is null and this map uses natural ordering, or its comparator does not permit null keys
IllegalArgumentException

public NavigableMap<K, V> subMap (K fromKey, boolean fromInclusive, K toKey, boolean toInclusive)

Returns a view of the portion of this map whose keys range from fromKey to toKey. If fromKey and toKey are equal, the returned map is empty unless fromInclusive and toInclusive are both true. The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports.

The returned map will throw an IllegalArgumentException on an attempt to insert a key outside of its range, or to construct a submap either of whose endpoints lie outside its range.

Parameters

fromKey	low endpoint of the keys in the returned map
fromInclusive	true if the low endpoint is to be included in the returned view
toKey	high endpoint of the keys in the returned map
toInclusive	true if the high endpoint is to be included in the returned view

Returns

• a view of the portion of this map whose keys range from fromKey to toKey

Throws

ClassCastException
NullPointerException	if fromKey or toKey is null and this map uses natural ordering, or its comparator does not permit null keys
IllegalArgumentException

public NavigableMap<K, V> tailMap (K fromKey, boolean inclusive)

Returns a view of the portion of this map whose keys are greater than (or equal to, if inclusive is true) fromKey. The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports.

The returned map will throw an IllegalArgumentException on an attempt to insert a key outside its range.

Parameters

fromKey	low endpoint of the keys in the returned map
inclusive	true if the low endpoint is to be included in the returned view

Returns

• a view of the portion of this map whose keys are greater than (or equal to, if inclusive is true) fromKey

Throws

ClassCastException
NullPointerException	if fromKey is null and this map uses natural ordering, or its comparator does not permit null keys
IllegalArgumentException

public SortedMap<K, V> tailMap (K fromKey)

Returns a view of the portion of this map whose keys are greater than or equal to fromKey. The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports.

The returned map will throw an IllegalArgumentException on an attempt to insert a key outside its range.

Equivalent to tailMap(fromKey, true).

Parameters

fromKey	low endpoint (inclusive) of the keys in the returned map

Returns

• a view of the portion of this map whose keys are greater than or equal to fromKey

Throws

ClassCastException
NullPointerException	if fromKey is null and this map uses natural ordering, or its comparator does not permit null keys
IllegalArgumentException

public Collection<V> values ()

Returns a Collection view of the values contained in this map.

The collection's iterator returns the values in ascending order of the corresponding keys. The collection's spliterator is late-binding, fail-fast, and additionally reports Spliterator.ORDERED with an encounter order that is ascending order of the corresponding keys.

The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa. If the map is modified while an iteration over the collection is in progress (except through the iterator's own remove operation), the results of the iteration are undefined. The collection supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Collection.remove, removeAll, retainAll and clear operations. It does not support the add or addAll operations.

Returns

• a collection view of the values contained in this map