java.util
Class Vector

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

Direct Known Subclasses:

Stack

public class Vector

extends AbstractList

implements List, 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 JDK1.2, 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.

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 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

void	add(int index, Object element) Inserts the specified element at the specified position in this Vector.
boolean	add(Object o) Appends the specified element to the end of this Vector.
boolean	addAll(Collection 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 c) Inserts all of the elements in in the specified Collection into this Vector at the specified position.
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.
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.
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.
boolean	equals(Object o) Compares the specified Object with this Vector for equality.
Object	firstElement() Returns the first component (the item at index 0) of this vector.
Object	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(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.
Object	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.
Object	set(int index, Object element) Replaces the element at the specified position in this Vector with the specified element.
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.
List	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.
Object[]	toArray(Object[] a) Returns an array containing all of the elements in this Vector in the correct order.
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

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 0, 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 c)

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

Since:

JDK1.2

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.

trimToSize

public void trimToSize()

Trims the capacity of this vector to be the vector's current size. If the capacity of this cector 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 nonpositive, 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 arary, 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 List

Overrides:

size in class AbstractCollection

Returns:

the number of components in this vector.

isEmpty

public boolean isEmpty()

Tests if this vector has no components.

Specified by:

isEmpty in interface List

Overrides:

isEmpty in class AbstractCollection

Returns:

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

elements

public Enumeration 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 List

Overrides:

contains in class AbstractCollection

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

Overrides:

indexOf in class AbstractList

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)

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.

Parameters:

elem - an object.

index - the index to start searching from.

Returns:

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

See Also:

Object.equals(Object)

lastIndexOf

public int lastIndexOf(Object elem)

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

Specified by:

lastIndexOf in interface List

Overrides:

lastIndexOf in class AbstractList

Parameters:

elem - the desired component.

Returns:

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

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.

Parameters:

elem - the desired component.

index - the index to start searching from.

Returns:

the index of the last occurrence of the specified object in this vector at position less than index in the vector, that is, the largest value k such that elem.equals(elementData[k]) && (k <= index) is true; -1 if the object is not found.

elementAt

public Object elementAt(int index)

Returns the component at the specified index.

This method is identical in functionality to the get 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 negative or not less than the current size of this Vector object. given.

See Also:

get(int), List

firstElement

public Object 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.

lastElement

public Object 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.

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.

This method is identical in functionality to the set 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 was invalid.

See Also:

size(), List, set(int, java.lang.Object)

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 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 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 was invalid.

See Also:

size(), remove(int), List

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. (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(Object, int) 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 was invalid.

See Also:

size(), add(int, Object), List

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.

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

Parameters:

obj - the component to be added.

See Also:

add(Object), List

removeElement

public 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.

See Also:

List.remove(Object), List

removeAllElements

public 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).

See Also:

clear(), List

clone

public 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.

Overrides:

clone in class Object

Returns:

a clone of this vector.

toArray

public Object[] toArray()

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

Specified by:

toArray in interface List

Overrides:

toArray in class AbstractCollection

Since:

JDK1.2

toArray

public Object[] toArray(Object[] 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.

Specified by:

toArray in interface List

Overrides:

toArray in class AbstractCollection

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 - the runtime type of a is not a supertype of the runtime type of every element in this Vector.

get

public Object get(int index)

Returns the element at the specified position in this Vector.

Specified by:

get in interface List

Overrides:

get in class AbstractList

Parameters:

index - index of element to return.

Throws:

ArrayIndexOutOfBoundsException - index is out of range (index < 0 || index >= size()).

Since:

JDK1.2

set

public Object set(int index,
                  Object element)

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

Specified by:

set in interface List

Overrides:

set in class AbstractList

Parameters:

index - index of element to replace.

element - element to be stored at the specified position.

Returns:

the element previously at the specified position.

Throws:

ArrayIndexOutOfBoundsException - index out of range (index < 0 || index >= size()).

IllegalArgumentException - fromIndex > toIndex.

Since:

JDK1.2

add

public boolean add(Object o)

Appends the specified element to the end of this Vector.

Specified by:

add in interface List

Overrides:

add in class AbstractList

Parameters:

o - element to be appended to this Vector.

Returns:

true (as per the general contract of Collection.add).

Since:

JDK1.2

remove

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).

Specified by:

remove in interface List

Overrides:

remove in class AbstractCollection

Parameters:

o - element to be removed from this Vector, if present.

Returns:

true if the Vector contained the specified element.

Since:

JDK1.2

add

public void add(int index,
                Object 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).

Specified by:

add in interface List

Overrides:

add in class AbstractList

Parameters:

index - index at which the specified element is to be inserted.

element - element to be inserted.

Throws:

ArrayIndexOutOfBoundsException - index is out of range (index < 0 || index > size()).

Since:

JDK1.2

remove

public Object 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.

Specified by:

remove in interface List

Overrides:

remove in class AbstractList

Parameters:

index - the index of the element to removed.

Throws:

ArrayIndexOutOfBoundsException - index out of range (index < 0 || index >= size()).

Since:

JDK1.2

clear

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).

Specified by:

clear in interface List

Overrides:

clear in class AbstractList

Since:

JDK1.2

containsAll

public boolean containsAll(Collection c)

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

Specified by:

containsAll in interface List

Overrides:

containsAll in class AbstractCollection

Returns:

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

addAll

public boolean addAll(Collection 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.)

Specified by:

addAll in interface List

Overrides:

addAll in class AbstractCollection

Parameters:

index - index at which to insert first element from the specified collection.

c - elements to be inserted into this Vector.

Throws:

ArrayIndexOutOfBoundsException - index out of range (index < 0 || index > size()).

Since:

JDK1.2

removeAll

public boolean removeAll(Collection c)

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

Specified by:

removeAll in interface List

Overrides:

removeAll in class AbstractCollection

Returns:

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

Since:

JDK1.2

retainAll

public 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.

Specified by:

retainAll in interface List

Overrides:

retainAll in class AbstractCollection

Returns:

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

Since:

JDK1.2

addAll

public boolean addAll(int index,
                      Collection c)

Inserts all of the elements in 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.

Specified by:

addAll in interface List

Overrides:

addAll in class AbstractList

Parameters:

index - index at which to insert first element from the specified collection.

c - elements to be inserted into this Vector.

Throws:

ArrayIndexOutOfBoundsException - index out of range (index < 0 || index > size()).

Since:

JDK1.2

equals

public 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.

Specified by:

equals in interface List

Overrides:

equals in class AbstractList

Parameters:

o - the Object to be compared for equality with this Vector.

Returns:

true if the specified Object is equal to this Vector

hashCode

public int hashCode()

Returns the hash code value for this Vector.

Specified by:

hashCode in interface List

Overrides:

hashCode in class AbstractList

Tags copied from interface: List

Returns:

the hash code value for this list.

See Also:

Object.hashCode(), Object.equals(Object), List.equals(Object)

toString

public String toString()

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

Overrides:

toString in class AbstractCollection

Tags copied from class: AbstractCollection

Returns:

a string representation of this collection.

subList

public List 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.)

Specified by:

subList in interface List

Overrides:

subList in class AbstractList

Parameters:

fromIndex - low endpoint (inclusive) of the subList.

toKey - high endpoint (exclusive) of the subList.

Returns:

a view of the specified range within this List.

Throws:

IndexOutOfBoundsException - endpoint index value out of range (fromIndex < 0 || toIndex > size)

IllegalArgumentException - endpoint indices out of order (fromIndex > toIndex)

removeRange

protected 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 ArrayList by (toIndex - fromIndex) elements. (If toIndex==fromIndex, this operation has no effect.)

Overrides:

removeRange in class AbstractList

Parameters:

fromIndex - index of first element to be removed.

fromIndex - index after last element to be removed.