Vector

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

Known Direct Subclasses Stack<E> Stack<E> The Stack class represents a last-in-first-out (LIFO) stack of objects.

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.

See Also

• Collection
• LinkedList

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

From class java.util.AbstractList

protected int

modCount

The number of times this list has been structurally modified.

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

From class java.util.AbstractList

void	add(int index, E element) Inserts the specified element at the specified position in this list (optional operation).
boolean	add(E e) Appends the specified element to the end of this list (optional operation).
boolean	addAll(int index, Collection<? extends E> c) Inserts all of the elements in the specified collection into this list at the specified position (optional operation).
void	clear() Removes all of the elements from this list (optional operation).
boolean	equals(Object o) Compares the specified object with this list for equality.
abstract E	get(int index) Returns the element at the specified position in this list.
int	hashCode() Returns the hash code value for this list.
int	indexOf(Object o) Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element.
Iterator<E>	iterator() Returns an iterator over the elements in this list in proper sequence.
int	lastIndexOf(Object o) Returns the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element.
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.
ListIterator<E>	listIterator() Returns a list iterator over the elements in this list (in proper sequence).
E	remove(int index) Removes the element at the specified position in this list (optional operation).
void	removeRange(int fromIndex, int toIndex) Removes from this list all of the elements whose index is between fromIndex, inclusive, and toIndex, exclusive.
E	set(int index, E element) Replaces the element at the specified position in this list with the specified element (optional operation).
List<E>	subList(int fromIndex, int toIndex) Returns a view of the portion of this list between the specified fromIndex, inclusive, and toIndex, exclusive.

From class java.util.AbstractCollection

boolean	add(E e) Ensures that this collection contains the specified element (optional operation). This implementation always throws an UnsupportedOperationException.
boolean	addAll(Collection<? extends E> c) Adds all of the elements in the specified collection to this collection (optional operation). This implementation iterates over the specified collection, and adds each object returned by the iterator to this collection, in turn.
void	clear() Removes all of the elements from this collection (optional operation). This implementation iterates over this collection, removing each element using the Iterator.remove operation.
boolean	contains(Object o) Returns true if this collection contains the specified element. This implementation iterates over the elements in the collection, checking each element in turn for equality with the specified element.
boolean	containsAll(Collection<?> c) Returns true if this collection contains all of the elements in the specified collection. This implementation iterates over the specified collection, checking each element returned by the iterator in turn to see if it's contained in this collection.
boolean	isEmpty() Returns true if this collection contains no elements. This implementation returns size() == 0.
abstract Iterator<E>	iterator() Returns an iterator over the elements contained in this collection.
boolean	remove(Object o) Removes a single instance of the specified element from this collection, if it is present (optional operation). This implementation iterates over the collection looking for the specified element.
boolean	removeAll(Collection<?> c) Removes all of this collection's elements that are also contained in the specified collection (optional operation). This implementation iterates over this collection, checking each element returned by the iterator in turn to see if it's contained in the specified collection.
boolean	retainAll(Collection<?> c) Retains only the elements in this collection that are contained in the specified collection (optional operation). This implementation iterates over this collection, checking each element returned by the iterator in turn to see if it's contained in the specified collection.
abstract int	size() Returns the number of elements in this collection.
<T> T[]	toArray(T[] contents) Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array. This implementation returns an array containing all the elements returned by this collection's iterator in the same order, stored in consecutive elements of the array, starting with index 0.
Object[]	toArray() Returns an array containing all of the elements in this collection. This implementation returns an array containing all the elements returned by this collection's iterator, in the same order, stored in consecutive elements of the array, starting with index 0.
String	toString() Returns a string representation of this collection.

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.List

abstract boolean	add(E e) Appends the specified element to the end of this list (optional operation).
abstract void	add(int index, E element) Inserts the specified element at the specified position in this list (optional operation).
abstract boolean	addAll(Collection<? extends E> c) Appends all of the elements in the specified collection to the end of this list, in the order that they are returned by the specified collection's iterator (optional operation).
abstract boolean	addAll(int index, Collection<? extends E> c) Inserts all of the elements in the specified collection into this list at the specified position (optional operation).
abstract void	clear() Removes all of the elements from this list (optional operation).
abstract boolean	contains(Object o) Returns true if this list contains the specified element.
abstract boolean	containsAll(Collection<?> c) Returns true if this list contains all of the elements of the specified collection.
abstract boolean	equals(Object o) Compares the specified object with this list for equality.
abstract E	get(int index) Returns the element at the specified position in this list.
abstract int	hashCode() Returns the hash code value for this list.
abstract int	indexOf(Object o) Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element.
abstract boolean	isEmpty() Returns true if this list contains no elements.
abstract Iterator<E>	iterator() Returns an iterator over the elements in this list in proper sequence.
abstract int	lastIndexOf(Object o) Returns the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element.
abstract 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.
abstract ListIterator<E>	listIterator() Returns a list iterator over the elements in this list (in proper sequence).
abstract E	remove(int index) Removes the element at the specified position in this list (optional operation).
abstract boolean	remove(Object o) Removes the first occurrence of the specified element from this list, if it is present (optional operation).
abstract boolean	removeAll(Collection<?> c) Removes from this list all of its elements that are contained in the specified collection (optional operation).
void	replaceAll(UnaryOperator<E> operator) Replaces each element of this list with the result of applying the operator to that element.
abstract boolean	retainAll(Collection<?> c) Retains only the elements in this list that are contained in the specified collection (optional operation).
abstract E	set(int index, E element) Replaces the element at the specified position in this list with the specified element (optional operation).
abstract int	size() Returns the number of elements in this list.
void	sort(Comparator<? super E> c) Sorts this list according to the order induced by the specified Comparator.
Spliterator<E>	spliterator() Creates a Spliterator over the elements in this list.
abstract List<E>	subList(int fromIndex, int toIndex) Returns a view of the portion of this list between the specified fromIndex, inclusive, and toIndex, exclusive.
abstract Object[]	toArray() Returns an array containing all of the elements in this list in proper sequence (from first to last element).
abstract <T> T[]	toArray(T[] a) Returns an array containing all of the elements in this list in proper sequence (from first to last element); the runtime type of the returned array is that of the specified array.

From interface java.util.Collection

abstract boolean	add(E e) Ensures that this collection contains the specified element (optional operation).
abstract boolean	addAll(Collection<? extends E> c) Adds all of the elements in the specified collection to this collection (optional operation).
abstract void	clear() Removes all of the elements from this collection (optional operation).
abstract boolean	contains(Object o) Returns true if this collection contains the specified element.
abstract boolean	containsAll(Collection<?> c) Returns true if this collection contains all of the elements in the specified collection.
abstract boolean	equals(Object o) Compares the specified object with this collection for equality.
abstract int	hashCode() Returns the hash code value for this collection.
abstract boolean	isEmpty() Returns true if this collection contains no elements.
abstract Iterator<E>	iterator() Returns an iterator over the elements in this collection.
Stream<E>	parallelStream() Returns a possibly parallel Stream with this collection as its source.
abstract boolean	remove(Object o) Removes a single instance of the specified element from this collection, if it is present (optional operation).
abstract boolean	removeAll(Collection<?> c) Removes all of this collection's elements that are also contained in the specified collection (optional operation).
boolean	removeIf(Predicate<? super E> filter) Removes all of the elements of this collection that satisfy the given predicate.
abstract boolean	retainAll(Collection<?> c) Retains only the elements in this collection that are contained in the specified collection (optional operation).
abstract int	size() Returns the number of elements in this collection.
Spliterator<E>	spliterator() Creates a Spliterator over the elements in this collection.
Stream<E>	stream() Returns a sequential Stream with this collection as its source.
abstract <T> T[]	toArray(T[] a) Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array.
abstract Object[]	toArray() Returns an array containing all of the elements in this collection.

From interface java.lang.Iterable

void	forEach(Consumer<? super T> action) Performs the given action for each element of the Iterable until all elements have been processed or the action throws an exception.
abstract Iterator<E>	iterator() Returns an iterator over elements of type T.
Spliterator<E>	spliterator() Creates a Spliterator over the elements described by this Iterable.

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

• true (as specified by Collection.add(E))

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

See Also

• toArray(Object[])

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

• Iterator

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

See Also

• Object.equals(Object)

public synchronized void insertElementAt (E obj, int index)

Inserts the specified object as a component in this vector at the specified index. Each component in this vector with an index greater or equal to the specified index is shifted upward to have an index one greater than the value it had previously.

The index must be a value greater than or equal to 0 and less than or equal to the current size of the vector. (If the index is equal to the current size of the vector, the new element is appended to the Vector.)

This method is identical in functionality to the add(int, E) method (which is part of the List interface). Note that the add method reverses the order of the parameters, to more closely match array usage.

Parameters

obj	the component to insert
index	where to insert the new component

Throws

ArrayIndexOutOfBoundsException	if the index is out of range (index < 0 || index > size())

public synchronized boolean isEmpty ()

Tests if this vector has no components.

Returns

• true if and only if this vector has no components, that is, its size is zero; false otherwise.

public synchronized Iterator<E> iterator ()

Returns an iterator over the elements in this list in proper sequence.

The returned iterator is fail-fast.

Returns

• an iterator over the elements in this list in proper sequence

public synchronized E lastElement ()

Returns the last component of the vector.

Returns

• the last component of the vector, i.e., the component at index size() - 1.

Throws

NoSuchElementException	if this vector is empty

public 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. More formally, returns the highest 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 last occurrence of the specified element in this vector, or -1 if this vector does not contain the element

public 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. More formally, returns the highest 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 backwards from

Returns

• the index of the last occurrence of the element at position less than or equal to index in this vector; -1 if the element is not found.

Throws

IndexOutOfBoundsException	if the specified index is greater than or equal to the current size of this vector

public 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. The specified index indicates the first element that would be returned by an initial call to next. An initial call to previous would return the element with the specified index minus one.

The returned list iterator is fail-fast.

Parameters

index	index of the first element to be returned from the list iterator (by a call to next)

Returns

• a list iterator over the elements in this list (in proper sequence), starting at the specified position in the list

Throws

IndexOutOfBoundsException

public synchronized ListIterator<E> listIterator ()

Returns a list iterator over the elements in this list (in proper sequence).

The returned list iterator is fail-fast.

Returns

• a list iterator over the elements in this list (in proper sequence)

See Also

• listIterator(int)

public 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. More formally, removes the element with the lowest index i such that (o==null ? get(i)==null : o.equals(get(i))) (if such an element exists).

Parameters

o	element to be removed from this Vector, if present

Returns

• true if the Vector contained the specified element

public synchronized E remove (int index)

Removes the element at the specified position in this Vector. Shifts any subsequent elements to the left (subtracts one from their indices). Returns the element that was removed from the Vector.

Parameters

index	the index of the element to be removed

Returns

• element that was removed

Throws

ArrayIndexOutOfBoundsException	if the index is out of range (index < 0 || index >= size())

public synchronized boolean removeAll (Collection<?> c)

Removes from this Vector all of its elements that are contained in the specified Collection.

Parameters

c	a collection of elements to be removed from the Vector

Returns

• true if this Vector changed as a result of the call

Throws

ClassCastException	if the types of one or more elements in this vector are incompatible with the specified collection (optional)
NullPointerException	if this vector contains one or more null elements and the specified collection does not support null elements (optional), or if the specified collection is null

public synchronized void removeAllElements ()

Removes all components from this vector and sets its size to zero.

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

public synchronized boolean removeElement (Object obj)

Removes the first (lowest-indexed) occurrence of the argument from this vector. If the object is found in this vector, each component in the vector with an index greater or equal to the object's index is shifted downward to have an index one smaller than the value it had previously.

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

Parameters

obj	the component to be removed

Returns

• true if the argument was a component of this vector; false otherwise.

public synchronized void removeElementAt (int index)

Deletes the component at the specified index. Each component in this vector with an index greater or equal to the specified index is shifted downward to have an index one smaller than the value it had previously. The size of this vector is decreased by 1.

The index must be a value greater than or equal to 0 and less than the current size of the vector.

This method is identical in functionality to the remove(int) method (which is part of the List interface). Note that the remove method returns the old value that was stored at the specified position.

Parameters

index	the index of the object to remove

Throws

ArrayIndexOutOfBoundsException	if the index is out of range (index < 0 || index >= size())

public synchronized boolean removeIf (Predicate<? super E> filter)

Removes all of the elements of this collection that satisfy the given predicate. Errors or runtime exceptions thrown during iteration or by the predicate are relayed to the caller.

Parameters

filter	a predicate which returns true for elements to be removed

Returns

• true if any elements were removed

public synchronized void replaceAll (UnaryOperator<E> operator)

Replaces each element of this list with the result of applying the operator to that element. Errors or runtime exceptions thrown by the operator are relayed to the caller.

Parameters

operator	the operator to apply to each element

public synchronized boolean retainAll (Collection<?> c)

Retains only the elements in this Vector that are contained in the specified Collection. In other words, removes from this Vector all of its elements that are not contained in the specified Collection.

Parameters

c	a collection of elements to be retained in this Vector (all other elements are removed)

Returns

• true if this Vector changed as a result of the call

Throws

ClassCastException	if the types of one or more elements in this vector are incompatible with the specified collection (optional)
NullPointerException	if this vector contains one or more null elements and the specified collection does not support null elements (optional), or if the specified collection is null

public synchronized E set (int index, E element)

Replaces the element at the specified position in this Vector with the specified element.

Parameters

index	index of the element to replace
element	element to be stored at the specified position

Returns

• the element previously at the specified position

Throws

ArrayIndexOutOfBoundsException	if the index is out of range (index < 0 || index >= size())

public synchronized void setElementAt (E obj, int index)

Sets the component at the specified index of this vector to be the specified object. The previous component at that position is discarded.

The index must be a value greater than or equal to 0 and less than the current size of the vector.

This method is identical in functionality to the set(int, E) method (which is part of the List interface). Note that the set method reverses the order of the parameters, to more closely match array usage. Note also that the set method returns the old value that was stored at the specified position.

Parameters

obj	what the component is to be set to
index	the specified index

Throws

ArrayIndexOutOfBoundsException	if the index is out of range (index < 0 || index >= size())

public synchronized void setSize (int newSize)

Sets the size of this vector. If the new size is greater than the current size, new null items are added to the end of the vector. If the new size is less than the current size, all components at index newSize and greater are discarded.

Parameters

newSize	the new size of this vector

Throws

ArrayIndexOutOfBoundsException	if the new size is negative

public synchronized int size ()

Returns the number of components in this vector.

Returns

• the number of components in this vector

public synchronized void sort (Comparator<? super E> c)

Sorts this list according to the order induced by the specified Comparator.

All elements in this 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).

If the specified comparator is null then all elements in this list must implement the Comparable interface and the elements' {@linkplain Comparable natural ordering} should be used.

This list must be modifiable, but need not be resizable.

For apps running on and targeting Android versions greater than Nougat (API level > 25), Collections.sort(List) delegates to this method. Such apps must not call Collections.sort(List) from this method. Instead, prefer not overriding this method at all. If you must override it, consider this implementation:

 @Override
 public void sort(Comparator<? super E> c) {
   Object[] elements = toArray();
   Arrays.sort(elements, c);
   ListIterator<E> iterator = (ListIterator<Object>) listIterator();
   for (Object element : elements) {
     iterator.next();
     iterator.set((E) element);
   }
 }
 

Parameters

c	the Comparator used to compare list elements. A null value indicates that the elements' {@linkplain Comparable natural ordering} should be used

public Spliterator<E> spliterator ()

Creates a late-binding and fail-fast Spliterator over the elements in this list.

The Spliterator reports Spliterator.SIZED, Spliterator.SUBSIZED, and Spliterator.ORDERED. Overriding implementations should document the reporting of additional characteristic values.

Returns

• a Spliterator over the elements in this list

public synchronized List<E> subList (int fromIndex, int toIndex)

Returns a view of the portion of this List between fromIndex, inclusive, and toIndex, exclusive. (If fromIndex and toIndex are equal, the returned List is empty.) The returned List is backed by this List, so changes in the returned List are reflected in this List, and vice-versa. The returned List supports all of the optional List operations supported by this List.

This method eliminates the need for explicit range operations (of the sort that commonly exist for arrays). Any operation that expects a List can be used as a range operation by operating on a subList view instead of a whole List. For example, the following idiom removes a range of elements from a List:

      list.subList(from, to).clear();
 

Similar idioms may be constructed for indexOf and lastIndexOf, and all of the algorithms in the Collections class can be applied to a subList.

The semantics of the List returned by this method become undefined if the backing list (i.e., this List) is structurally modified in any way other than via the returned List. (Structural modifications are those that change the size of the List, or otherwise perturb it in such a fashion that iterations in progress may yield incorrect results.)

Parameters

fromIndex	low endpoint (inclusive) of the subList
toIndex	high endpoint (exclusive) of the subList

Returns

• a view of the specified range within this List

Throws

IndexOutOfBoundsException	if an endpoint index value is out of range (fromIndex < 0 || toIndex > size)
IllegalArgumentException	if the endpoint indices are out of order (fromIndex > toIndex)

public synchronized Object[] toArray ()

Returns an array containing all of the elements in this Vector in the correct order.

Returns

• an array containing all of the elements in this collection

public synchronized 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. If the Vector fits in the specified array, it is returned therein. Otherwise, a new array is allocated with the runtime type of the specified array and the size of this Vector.

If the Vector fits in the specified array with room to spare (i.e., the array has more elements than the Vector), the element in the array immediately following the end of the Vector is set to null. (This is useful in determining the length of the Vector only if the caller knows that the Vector does not contain any null elements.)

Parameters

a	the array into which the elements of the Vector are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose.

Returns

• an array containing the elements of the Vector

Throws

ArrayStoreException	if the runtime type of a is not a supertype of the runtime type of every element in this Vector
NullPointerException	if the given array is null

public synchronized String toString ()

Returns a string representation of this Vector, containing the String representation of each element.

Returns

• a string representation of this collection

public synchronized void trimToSize ()

Trims the capacity of this vector to be the vector's current size. If the capacity of this vector is larger than its current size, then the capacity is changed to equal the size by replacing its internal data array, kept in the field elementData, with a smaller one. An application can use this operation to minimize the storage of a vector.

Protected Methods

protected synchronized void removeRange (int fromIndex, int toIndex)

Removes from this list all of the elements whose index is between fromIndex, inclusive, and toIndex, exclusive. Shifts any succeeding elements to the left (reduces their index). This call shortens the list by (toIndex - fromIndex) elements. (If toIndex==fromIndex, this operation has no effect.)

Parameters

fromIndex	index of first element to be removed
toIndex	index after last element to be removed