java.util
Class Vector

java.lang.Object
  java.util.Vector

Direct Known Subclasses:

Stack

public class Vector
extends Object

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.

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 the vector.
protected Object[]	elementData The array buffer into which the components of the vector are stored.

Constructor Summary

Vector()
Constructs an empty vector.

Vector(int initialCapacity)
Constructs an empty vector with the specified initial capacity.

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

Method Summary

void	addElement(Object 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.
boolean	contains(Object elem) Tests if the specified object is a component in this vector.
void	copyInto(Object[] anArray) Copies the components of this vector into the specified array.
Object	elementAt(int index) Returns the component at the specified index.
Enumeration	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.
Object	firstElement() Returns the first component of 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(Object 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.
Object	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.
void	removeAllElements() Removes all components from this vector and sets its size to zero.
boolean	removeElement(Object obj) Removes the first occurrence of the argument from this vector.
void	removeElementAt(int index) Deletes the component at the specified index.
void	setElementAt(Object 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.
String	toString() Returns a string representation of this vector.
void	trimToSize() Trims the capacity of this vector to be the vector's current size.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

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 0, the capacity of the vector is doubled each time it needs to grow.

elementCount

protected int elementCount

The number of valid components in the vector.

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.

Constructor Detail

Vector

public Vector()

Constructs an empty vector.

Vector

public Vector(int initialCapacity)

Constructs an empty vector with the specified initial capacity.

Vector

public Vector(int initialCapacity,
              int capacityIncrement)

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

Method Detail

addElement

public void addElement(Object 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.

capacity

public int capacity()

Returns the current capacity of this vector.

contains

public boolean contains(Object elem)

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

copyInto

public void copyInto(Object[] anArray)

Copies the components of this vector into the specified array. The array must be big enough to hold all the objects in this vector. J2SE 1.4 : 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.

elementAt

public Object elementAt(int index)

Returns the component at the specified index.

elements

public Enumeration elements()

Returns an enumeration of the components of this 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.

firstElement

public Object firstElement()

Returns the first component of this vector.

indexOf

public int indexOf(Object elem)

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

indexOf

public 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. spec J2SE : Returns -1 if index >= the current size of this Vector. Throws: IndexOutOfBoundsException - if index is negative.

insertElementAt

public void insertElementAt(Object 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.

isEmpty

public boolean isEmpty()

Tests if this vector has no components.

lastElement

public Object lastElement()

Returns the last component of the vector.

lastIndexOf

public int lastIndexOf(Object elem)

Returns the index of the last occurrence of the specified object in this vector.

lastIndexOf

public int lastIndexOf(Object elem,
                       int index)

Searches backwards for the specified object, starting from the specified index, and returns an index to it.

removeAllElements

public void removeAllElements()

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

removeElement

public boolean removeElement(Object obj)

Removes the first 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.

Parameters:

obj - the component to be removed.

Returns:

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

removeElementAt

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

setElementAt

public void setElementAt(Object 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.

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.

size

public int size()

Returns the number of components in this vector.

toString

public String toString()

Returns a string representation of this vector.

Overrides:

toString in class Object

trimToSize

public void trimToSize()

Trims the capacity of this vector to be the vector's current size. An application can use this operation to minimize the storage of a vector.