java.util
Class Vector<E>

java.lang.Object   
  java.util.AbstractCollection   <E>
      java.util.AbstractList   <E>
          java.util.Vector<E>

All Implemented Interfaces:

Serializable , Cloneable , Iterable <E>, Collection <E>, List <E>, RandomAccess

Direct Known Subclasses:

Stack

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

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.

As of the Java 2 platform v1.2, this class has been retrofitted to implement List, so that it becomes a part of Java's collection framework. Unlike the new collection implementations, Vector is synchronized.

The Iterators returned by Vector'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 Vector's 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.

This class is a member of the Java Collections Framework.

Since:

JDK1.0

See Also:

Collection , List , ArrayList , LinkedList , Serialized Form

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.

Fields inherited from class java.util.AbstractList

modCount

Constructor Summary

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.

Vector (int initialCapacity)
Constructs an empty vector with the specified initial capacity and with its capacity increment equal to zero.

Vector (int initialCapacity, int capacityIncrement)
Constructs an empty vector with the specified initial capacity and capacity increment.

Method Summary

boolean	add (E o) Appends the specified element to the end of this Vector.
void	add (int index, E element) Inserts the specified element at the specified position in this Vector.
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.
boolean	addAll (int index, Collection <? extends E> c) Inserts all of the elements in the specified Collection into this Vector at the specified position.
void	addElement (E obj) Adds the specified component to the end of this vector, increasing its size by one.
int	capacity () Returns the current capacity of this vector.
void	clear () Removes all of the elements from this Vector.
Object	clone () Returns a clone of this vector.
boolean	contains (Object elem) Tests if the specified object is a component in this vector.
boolean	containsAll (Collection <?> c) Returns true if this Vector contains all of the elements in the specified Collection.
void	copyInto (Object [] anArray) Copies the components of this vector into the specified array.
E	elementAt (int index) Returns the component at the specified index.
Enumeration <E>	elements () Returns an enumeration of the components of this vector.
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.
boolean	equals (Object o) Compares the specified Object with this Vector for equality.
E	firstElement () Returns the first component (the item at index 0) of this vector.
E	get (int index) Returns the element at the specified position in this Vector.
int	hashCode () Returns the hash code value for this Vector.
int	indexOf (Object elem) Searches for the first occurence of the given argument, testing for equality using the equals method.
int	indexOf (Object elem, int index) Searches for the first occurence of the given argument, beginning the search at index, and testing for equality using the equals method.
void	insertElementAt (E obj, int index) Inserts the specified object as a component in this vector at the specified index.
boolean	isEmpty () Tests if this vector has no components.
E	lastElement () Returns the last component of the vector.
int	lastIndexOf (Object elem) Returns the index of the last occurrence of the specified object in this vector.
int	lastIndexOf (Object elem, int index) Searches backwards for the specified object, starting from the specified index, and returns an index to it.
E	remove (int index) Removes the element at the specified position in this Vector.
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.
boolean	removeAll (Collection <?> c) Removes from this Vector all of its elements that are contained in the specified Collection.
void	removeAllElements () Removes all components from this vector and sets its size to zero.
boolean	removeElement (Object obj) Removes the first (lowest-indexed) occurrence of the argument from this vector.
void	removeElementAt (int index) Deletes the component at the specified index.
protected void	removeRange (int fromIndex, int toIndex) Removes from this List all of the elements whose index is between fromIndex, inclusive and toIndex, exclusive.
boolean	retainAll (Collection <?> c) Retains only the elements in this Vector that are contained in the specified Collection.
E	set (int index, E element) Replaces the element at the specified position in this Vector with the specified element.
void	setElementAt (E obj, int index) Sets the component at the specified index of this vector to be the specified object.
void	setSize (int newSize) Sets the size of this vector.
int	size () Returns the number of components in this vector.
List <E>	subList (int fromIndex, int toIndex) Returns a view of the portion of this List between fromIndex, inclusive, and toIndex, exclusive.
Object []	toArray () Returns an array containing all of the elements in this Vector in the correct order.
<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.
String	toString () Returns a string representation of this Vector, containing the String representation of each element.
void	trimToSize () Trims the capacity of this vector to be the vector's current size.

Methods inherited from class java.util.AbstractList

iterator , listIterator , listIterator

Methods inherited from class java.lang.Object

finalize , getClass , notify , notifyAll , wait , wait , wait

Methods inherited from interface java.util.List

iterator , listIterator , listIterator

Field Detail

elementData

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.

elementCount

protected int elementCount

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

capacityIncrement

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.

Constructor Detail

Vector

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

Vector

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

Vector

public Vector()

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

Vector

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.

Since:

1.2

Method Detail

copyInto

public 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. The array must be big enough to hold all the objects in this vector, else an IndexOutOfBoundsException is thrown.

Parameters:

anArray - the array into which the components get copied.

Throws:

NullPointerException - if the given array is null.

trimToSize

public 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.

ensureCapacity

public 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.

setSize

public 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 new size is negative.

capacity

public 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).

size

public int size()

Returns the number of components in this vector.

Specified by:

size in interface Collection <E>

Specified by:

size in interface List <E>

Specified by:

size in class AbstractCollection <E>

Returns:

the number of components in this vector.

isEmpty

public boolean isEmpty()

Tests if this vector has no components.

Specified by:

isEmpty in interface Collection <E>

Specified by:

isEmpty in interface List <E>

Overrides:

isEmpty in class AbstractCollection <E>

Returns:

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

elements

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:

Enumeration , Iterator

contains

public boolean contains(Object    elem)

Tests if the specified object is a component in this vector.

Specified by:

contains in interface Collection <E>

Specified by:

contains in interface List <E>

Overrides:

contains in class AbstractCollection <E>

Parameters:

elem - an object.

Returns:

true if and only if the specified object is the same as a component in this vector, as determined by the equals method; false otherwise.

indexOf

public int indexOf(Object    elem)

Searches for the first occurence of the given argument, testing for equality using the equals method.

Specified by:

indexOf in interface List <E>

Overrides:

indexOf in class AbstractList <E>

Parameters:

elem - an object.

Returns:

the index of the first occurrence of the argument in this vector, that is, the smallest value k such that elem.equals(elementData[k]) is true; returns -1 if the object is not found.

See Also:

Object.equals(Object)