java.util
Class Vector

java.lang.Object
  |
  +--java.util.Vector

All Implemented Interfaces:

Cloneable

Direct Known Subclasses:

Stack

public class Vector

extends Object

implements Cloneable

Vector class (a growable array).

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 elements are added to the vector, the vector's storage increases in chunks the size of capacityIncrement. Setting the capacity to what you want before inserting a large number of objects will reduce the amount of incremental reallocation. You can safely ignore the capacity and the vector will still work correctly.

Field Summary

protected int	capacityIncrement The size of the increment.
protected int	elementCount The number of elements in the buffer.
protected Object[]	elementData The buffer where elements are stored.

Constructor Summary

Vector()
Constructs an empty vector.

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

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

Method Summary

void	addElement(Object obj) Adds the specified object as the last element of the vector.
int	capacity() Returns the current capacity of the vector.
Object	clone() Clones this vector.
boolean	contains(Object elem) Returns true if the specified object is a value of the collection.
void	copyInto(Object[] anArray) Copies the elements of this vector into the specified array.
Object	elementAt(int index) Returns the element at the specified index.
Enumeration	elements() Returns an enumeration of the elements.
void	ensureCapacity(int minCapacity) Ensures that the vector has at least the specified capacity.
Object	firstElement() Returns the first element of the sequence.
int	indexOf(Object elem) Searches for the specified object, starting from the first position and returns an index to it.
int	indexOf(Object elem, int index) Searches for the specified object, starting at the specified position and returns an index to it.
void	insertElementAt(Object obj, int index) Inserts the specified object as an element at the specified index.
boolean	isEmpty() Returns true if the collection contains no values.
Object	lastElement() Returns the last element of the sequence.
int	lastIndexOf(Object elem) Searches backwards for the specified object, starting from the last position and returns an index to it.
int	lastIndexOf(Object elem, int index) Searches backwards for the specified object, starting from the specified position and returns an index to it.
void	removeAllElements() Removes all elements of the vector.
boolean	removeElement(Object obj) Removes the element from the vector.
void	removeElementAt(int index) Deletes the element at the specified index.
void	setElementAt(Object obj, int index) Sets the element at the specified index to be the specified object.
void	setSize(int newSize) Sets the size of the vector.
int	size() Returns the number of elements in the vector.
String	toString() Converts the vector to a string.
void	trimToSize() Trims the vector's capacity down to size.

Methods inherited from class java.lang.Object

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

Field Detail

elementData

protected Object[] elementData

The buffer where elements are stored.

elementCount

protected int elementCount

The number of elements in the buffer.

capacityIncrement

protected int capacityIncrement

The size of the increment. If it is 0 the size of the the buffer is doubled everytime it needs to grow.

Constructor Detail

Vector

public Vector(int initialCapacity,
              int capacityIncrement)

Constructs an empty vector with the specified storage capacity and the specified capacityIncrement.

Parameters:

initialCapacity - the initial storage capacity of the vector

capacityIncrement - how much to increase the element's size by.

Vector

public Vector(int initialCapacity)

Constructs an empty vector with the specified storage capacity.

Parameters:

initialCapacity - the initial storage capacity of the vector

Vector

public Vector()

Constructs an empty vector.

Method Detail

copyInto

public final void copyInto(Object[] anArray)

Copies the elements of this vector into the specified array.

Parameters:

anArray - the array where elements get copied into

trimToSize

public final void trimToSize()

Trims the vector's capacity down to size. Use this operation to minimize the storage of a vector. Subsequent insertions will cause reallocation.

ensureCapacity

public final void ensureCapacity(int minCapacity)

Ensures that the vector has at least the specified capacity.

Parameters:

minCapacity - the desired minimum capacity

setSize

public final void setSize(int newSize)

Sets the size of the vector. If the size shrinks, the extra elements (at the end of the vector) are lost; if the size increases, the new elements are set to null.

Parameters:

newSize - the new size of the vector

capacity

public final int capacity()

Returns the current capacity of the vector.

size

public final int size()

Returns the number of elements in the vector. Note that this is not the same as the vector's capacity.

isEmpty

public final boolean isEmpty()

Returns true if the collection contains no values.

elements

public final Enumeration elements()

Returns an enumeration of the elements. Use the Enumeration methods on the returned object to fetch the elements sequentially.

contains

public final boolean contains(Object elem)

Returns true if the specified object is a value of the collection.

Parameters:

elem - the desired element

indexOf

public final int indexOf(Object elem)

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

Parameters:

elem - the desired element

Returns:

the index of the element, or -1 if it was not found.

indexOf

public final int indexOf(Object elem,
                         int index)

Searches for the specified object, starting at the specified position and returns an index to it.

Parameters:

elem - the desired element

index - the index where to start searching

Returns:

the index of the element, or -1 if it was not found.

lastIndexOf

public final int lastIndexOf(Object elem)

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

Parameters:

elem - the desired element

Returns:

the index of the element, or -1 if it was not found.

lastIndexOf

public final int lastIndexOf(Object elem,
                             int index)

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

Parameters:

elem - the desired element

index - the index where to start searching

Returns:

the index of the element, or -1 if it was not found.

elementAt

public final Object elementAt(int index)

Returns the element at the specified index.

Parameters:

index - the index of the desired element

Throws:

ArrayIndexOutOfBoundsException - If an invalid index was given.

firstElement

public final Object firstElement()

Returns the first element of the sequence.

Throws:

NoSuchElementException - If the sequence is empty.

lastElement

public final Object lastElement()

Returns the last element of the sequence.

Throws:

NoSuchElementException - If the sequence is empty.

setElementAt

public final void setElementAt(Object obj,
                               int index)

Sets the element at the specified index to be the specified object. The previous element at that position is discarded.

Parameters:

obj - what the element is to be set to

index - the specified index

Throws:

ArrayIndexOutOfBoundsException - If the index was invalid.

removeElementAt

public final void removeElementAt(int index)

Deletes the element at the specified index. Elements with an index greater than the current index are moved down.

Parameters:

index - the element to remove

Throws:

ArrayIndexOutOfBoundsException - If the index was invalid.

insertElementAt

public final void insertElementAt(Object obj,
                                  int index)

Inserts the specified object as an element at the specified index. Elements with an index greater or equal to the current index are shifted up.

Parameters:

obj - the element to insert

index - where to insert the new element

Throws:

ArrayIndexOutOfBoundsException - If the index was invalid.

addElement

public final void addElement(Object obj)

Adds the specified object as the last element of the vector.

Parameters:

obj - the element to be added

removeElement

public final boolean removeElement(Object obj)

Removes the element from the vector. If the object occurs more than once, only the first is removed. If the object is not an element, returns false.

Parameters:

obj - the element to be removed

Returns:

true if the element was actually removed; false otherwise.

removeAllElements

public final void removeAllElements()

Removes all elements of the vector. The vector becomes empty.

clone

public Object clone()

Clones this vector. The elements are not cloned.

Overrides:

clone in class Object

Returns:

a clone of this Object.

toString

public final String toString()

Converts the vector to a string. Useful for debugging.

Overrides:

toString in class Object