Vector

public class Vector extends AbstractList<E>
implements List<E> RandomAccess Cloneable Serializable
Known Direct Subclasses

The Vector class implements a growable array of objects. Like an array, it contains components that can be accessed using an integer index. However, the size of a Vector can grow or shrink as needed to accommodate adding and removing items after the Vector has been created.

Each vector tries to optimize storage management by maintaining a capacity and a capacityIncrement. The capacity is always at least as large as the vector size; it is usually larger because as components are added to the vector, the vector's storage increases in chunks the size of capacityIncrement. An application can increase the capacity of a vector before inserting a large number of components; this reduces the amount of incremental reallocation.

The iterators returned by this class's iterator and listIterator methods are fail-fast: if the vector is structurally modified at any time after the iterator is created, in any way except through the iterator's own remove or add methods, 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. The Enumerations returned by the elements method are not fail-fast.

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.

As of the Java 2 platform v1.2, this class was retrofitted to implement the List interface, making it a member of the Java Collections Framework. Unlike the new collection implementations, Vector is synchronized. If a thread-safe implementation is not needed, it is recommended to use ArrayList in place of Vector.

Field Summary

protected int capacityIncrement The amount by which the capacity of the vector is automatically incremented when its size becomes greater than its capacity.
protected int elementCount The number of valid components in this Vector object.
protected Object[] elementData The array buffer into which the components of the vector are stored.

Inherited Field Summary

Public Constructor Summary

Vector(int initialCapacity, int capacityIncrement)
Constructs an empty vector with the specified initial capacity and capacity increment.
Vector(int initialCapacity)
Constructs an empty vector with the specified initial capacity and with its capacity increment equal to zero.
Vector()
Constructs an empty vector so that its internal data array has size 10 and its standard capacity increment is zero.
Vector(Collection<? extends E> c)
Constructs a vector containing the elements of the specified collection, in the order they are returned by the collection's iterator.

Public Method Summary

void
add(int index, E element)
Inserts the specified element at the specified position in this Vector.
synchronized boolean
add(E e)
Appends the specified element to the end of this Vector.
synchronized boolean
addAll(int index, Collection<? extends E> c)
Inserts all of the elements in the specified Collection into this Vector at the specified position.
synchronized boolean
addAll(Collection<? extends E> c)
Appends all of the elements in the specified Collection to the end of this Vector, in the order that they are returned by the specified Collection's Iterator.
synchronized void
addElement(E obj)
Adds the specified component to the end of this vector, increasing its size by one.
synchronized int
capacity()
Returns the current capacity of this vector.
void
clear()
Removes all of the elements from this Vector.
synchronized Object
clone()
Returns a clone of this vector.
boolean
contains(Object o)
Returns true if this vector contains the specified element.
synchronized boolean
containsAll(Collection<?> c)
Returns true if this Vector contains all of the elements in the specified Collection.
synchronized void
copyInto(Object[] anArray)
Copies the components of this vector into the specified array.
synchronized E
elementAt(int index)
Returns the component at the specified index.
Enumeration<E>
elements()
Returns an enumeration of the components of this vector.
synchronized void
ensureCapacity(int minCapacity)
Increases the capacity of this vector, if necessary, to ensure that it can hold at least the number of components specified by the minimum capacity argument.
synchronized boolean
equals(Object o)
Compares the specified Object with this Vector for equality.
synchronized E
firstElement()
Returns the first component (the item at index 0) of this vector.
synchronized void
forEach(Consumer<? super E> action)
synchronized E
get(int index)
Returns the element at the specified position in this Vector.
synchronized int
hashCode()
Returns the hash code value for this Vector.
int
indexOf(Object o)
Returns the index of the first occurrence of the specified element in this vector, or -1 if this vector does not contain the element.
synchronized int
indexOf(Object o, int index)
Returns the index of the first occurrence of the specified element in this vector, searching forwards from index, or returns -1 if the element is not found.
synchronized void
insertElementAt(E obj, int index)
Inserts the specified object as a component in this vector at the specified index.
synchronized boolean
isEmpty()
Tests if this vector has no components.
synchronized Iterator<E>
iterator()
Returns an iterator over the elements in this list in proper sequence.
synchronized E
lastElement()
Returns the last component of the vector.
synchronized int
lastIndexOf(Object o)
Returns the index of the last occurrence of the specified element in this vector, or -1 if this vector does not contain the element.
synchronized int
lastIndexOf(Object o, int index)
Returns the index of the last occurrence of the specified element in this vector, searching backwards from index, or returns -1 if the element is not found.
synchronized ListIterator<E>
listIterator(int index)
Returns a list iterator over the elements in this list (in proper sequence), starting at the specified position in the list.
synchronized ListIterator<E>
listIterator()
Returns a list iterator over the elements in this list (in proper sequence).
boolean
remove(Object o)
Removes the first occurrence of the specified element in this Vector If the Vector does not contain the element, it is unchanged.
synchronized E
remove(int index)
Removes the element at the specified position in this Vector.
synchronized boolean
removeAll(Collection<?> c)
Removes from this Vector all of its elements that are contained in the specified Collection.
synchronized void
removeAllElements()
Removes all components from this vector and sets its size to zero.
synchronized boolean
removeElement(Object obj)
Removes the first (lowest-indexed) occurrence of the argument from this vector.
synchronized void
removeElementAt(int index)
Deletes the component at the specified index.
synchronized boolean
removeIf(Predicate<? super E> filter)
Removes all of the elements of this collection that satisfy the given predicate.
synchronized void
replaceAll(UnaryOperator<E> operator)
Replaces each element of this list with the result of applying the operator to that element.
synchronized boolean
retainAll(Collection<?> c)
Retains only the elements in this Vector that are contained in the specified Collection.
synchronized E
set(int index, E element)
Replaces the element at the specified position in this Vector with the specified element.
synchronized void
setElementAt(E obj, int index)
Sets the component at the specified index of this vector to be the specified object.
synchronized void
setSize(int newSize)
Sets the size of this vector.
synchronized int
size()
Returns the number of components in this vector.
synchronized void
sort(Comparator<? super E> c)
Sorts this list according to the order induced by the specified Comparator.
Spliterator<E>
spliterator()
Creates a late-binding and fail-fast Spliterator over the elements in this list.
synchronized List<E>
subList(int fromIndex, int toIndex)
Returns a view of the portion of this List between fromIndex, inclusive, and toIndex, exclusive.
synchronized Object[]
toArray()
Returns an array containing all of the elements in this Vector in the correct order.
synchronized <T> T[]
toArray(T[] a)
Returns an array containing all of the elements in this Vector in the correct order; the runtime type of the returned array is that of the specified array.
synchronized String
toString()
Returns a string representation of this Vector, containing the String representation of each element.
synchronized void
trimToSize()
Trims the capacity of this vector to be the vector's current size.

Protected Method Summary

synchronized void
removeRange(int fromIndex, int toIndex)
Removes from this list all of the elements whose index is between fromIndex, inclusive, and toIndex, exclusive.

Inherited Method Summary

Fields

protected int capacityIncrement

The amount by which the capacity of the vector is automatically incremented when its size becomes greater than its capacity. If the capacity increment is less than or equal to zero, the capacity of the vector is doubled each time it needs to grow.

protected int elementCount

The number of valid components in this Vector object. Components elementData[0] through elementData[elementCount-1] are the actual items.

protected Object[] elementData

The array buffer into which the components of the vector are stored. The capacity of the vector is the length of this array buffer, and is at least large enough to contain all the vector's elements.

Any array elements following the last element in the Vector are null.

Public Constructors

public Vector (int initialCapacity, int capacityIncrement)

Constructs an empty vector with the specified initial capacity and capacity increment.

Parameters
initialCapacity the initial capacity of the vector
capacityIncrement the amount by which the capacity is increased when the vector overflows
Throws
IllegalArgumentException if the specified initial capacity is negative

public Vector (int initialCapacity)

Constructs an empty vector with the specified initial capacity and with its capacity increment equal to zero.

Parameters
initialCapacity the initial capacity of the vector
Throws
IllegalArgumentException if the specified initial capacity is negative

public Vector ()

Constructs an empty vector so that its internal data array has size 10 and its standard capacity increment is zero.

public Vector (Collection<? extends E> c)

Constructs a vector containing the elements of the specified collection, in the order they are returned by the collection's iterator.

Parameters
c the collection whose elements are to be placed into this vector
Throws
NullPointerException if the specified collection is null

Public Methods

public void add (int index, E element)

Inserts the specified element at the specified position in this Vector. Shifts the element currently at that position (if any) and any subsequent elements to the right (adds one to their indices).

Parameters
index index at which the specified element is to be inserted
element element to be inserted
Throws
ArrayIndexOutOfBoundsException if the index is out of range (index < 0 || index > size())

public synchronized boolean add (E e)

Appends the specified element to the end of this Vector.

Parameters
e element to be appended to this Vector
Returns

public synchronized boolean addAll (int index, Collection<? extends E> c)

Inserts all of the elements in the specified Collection into this Vector at the specified position. Shifts the element currently at that position (if any) and any subsequent elements to the right (increases their indices). The new elements will appear in the Vector in the order that they are returned by the specified Collection's iterator.

Parameters
index index at which to insert the first element from the specified collection
c elements to be inserted into this Vector
Returns
  • true if this Vector changed as a result of the call
Throws
ArrayIndexOutOfBoundsException if the index is out of range (index < 0 || index > size())
NullPointerException if the specified collection is null

public synchronized boolean addAll (Collection<? extends E> c)

Appends all of the elements in the specified Collection to the end of this Vector, in the order that they are returned by the specified Collection's Iterator. The behavior of this operation is undefined if the specified Collection is modified while the operation is in progress. (This implies that the behavior of this call is undefined if the specified Collection is this Vector, and this Vector is nonempty.)

Parameters
c elements to be inserted into this Vector
Returns
  • true if this Vector changed as a result of the call
Throws
NullPointerException if the specified collection is null

public synchronized void addElement (E obj)

Adds the specified component to the end of this vector, increasing its size by one. The capacity of this vector is increased if its size becomes greater than its capacity.

This method is identical in functionality to the add(E) method (which is part of the List interface).

Parameters
obj the component to be added

public synchronized int capacity ()

Returns the current capacity of this vector.

Returns
  • the current capacity (the length of its internal data array, kept in the field elementData of this vector)

public void clear ()

Removes all of the elements from this Vector. The Vector will be empty after this call returns (unless it throws an exception).

public synchronized Object clone ()

Returns a clone of this vector. The copy will contain a reference to a clone of the internal data array, not a reference to the original internal data array of this Vector object.

Returns
  • a clone of this vector

public boolean contains (Object o)

Returns true if this vector contains the specified element. More formally, returns true if and only if this vector contains at least one element e such that (o==null ? e==null : o.equals(e)).

Parameters
o element whose presence in this vector is to be tested
Returns
  • true if this vector contains the specified element

public synchronized boolean containsAll (Collection<?> c)

Returns true if this Vector contains all of the elements in the specified Collection.

Parameters
c a collection whose elements will be tested for containment in this Vector
Returns
  • true if this Vector contains all of the elements in the specified collection
Throws
NullPointerException if the specified collection is null

public synchronized void copyInto (Object[] anArray)

Copies the components of this vector into the specified array. The item at index k in this vector is copied into component k of anArray.

Parameters
anArray the array into which the components get copied
Throws
NullPointerException if the given array is null
IndexOutOfBoundsException if the specified array is not large enough to hold all the components of this vector
ArrayStoreException if a component of this vector is not of a runtime type that can be stored in the specified array

public synchronized E elementAt (int index)

Returns the component at the specified index.

This method is identical in functionality to the get(int) method (which is part of the List interface).

Parameters
index an index into this vector
Returns
  • the component at the specified index
Throws
ArrayIndexOutOfBoundsException if the index is out of range (index < 0 || index >= size())

public Enumeration<E> elements ()

Returns an enumeration of the components of this vector. The returned Enumeration object will generate all items in this vector. The first item generated is the item at index 0, then the item at index 1, and so on.

Returns
  • an enumeration of the components of this vector
See Also

public synchronized void ensureCapacity (int minCapacity)

Increases the capacity of this vector, if necessary, to ensure that it can hold at least the number of components specified by the minimum capacity argument.

If the current capacity of this vector is less than minCapacity, then its capacity is increased by replacing its internal data array, kept in the field elementData, with a larger one. The size of the new data array will be the old size plus capacityIncrement, unless the value of capacityIncrement is less than or equal to zero, in which case the new capacity will be twice the old capacity; but if this new size is still smaller than minCapacity, then the new capacity will be minCapacity.

Parameters
minCapacity the desired minimum capacity

public synchronized boolean equals (Object o)

Compares the specified Object with this Vector for equality. Returns true if and only if the specified Object is also a List, both Lists have the same size, and all corresponding pairs of elements in the two Lists are equal. (Two elements e1 and e2 are equal if (e1==null ? e2==null : e1.equals(e2)).) In other words, two Lists are defined to be equal if they contain the same elements in the same order.

Parameters
o the Object to be compared for equality with this Vector
Returns
  • true if the specified Object is equal to this Vector

public synchronized E firstElement ()

Returns the first component (the item at index 0) of this vector.

Returns
  • the first component of this vector
Throws
NoSuchElementException if this vector has no components

public synchronized void forEach (Consumer<? super E> action)

Parameters
action

public synchronized E get (int index)

Returns the element at the specified position in this Vector.

Parameters
index index of the element to return
Returns
  • object at the specified index
Throws
ArrayIndexOutOfBoundsException if the index is out of range (index < 0 || index >= size())

public synchronized int hashCode ()

Returns the hash code value for this Vector.

Returns
  • the hash code value for this list

public int indexOf (Object o)

Returns the index of the first occurrence of the specified element in this vector, or -1 if this vector does not contain the element. More formally, returns the lowest index i such that (o==null ? get(i)==null : o.equals(get(i))), or -1 if there is no such index.

Parameters
o element to search for
Returns
  • the index of the first occurrence of the specified element in this vector, or -1 if this vector does not contain the element

public synchronized int indexOf (Object o, int index)

Returns the index of the first occurrence of the specified element in this vector, searching forwards from index, or returns -1 if the element is not found. More formally, returns the lowest index i such that (i >= index && (o==null ? get(i)==null : o.equals(get(i)))), or -1 if there is no such index.

Parameters
o element to search for
index index to start searching from
Returns
  • the index of the first occurrence of the element in this vector at position index or later in the vector; -1 if the element is not found.
Throws
IndexOutOfBoundsException if the specified index is negative

public synchronized void insertElementAt