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Class java.util.Vector

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

Field Summary
int  capacityIncrement
The amount by which the capacity of the vector is automatically incremented when its size becomes greater than its capacity.
int  elementCount
The number of valid components in this Vector object.
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(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 c)
Constructs a vector containing the elements of the specified collection, in the order they are returned by the collection's iterator.
 

Method Summary
void  add(int index, Object element)
Inserts the specified element at the specified position in this Vector.
boolean  addAll(Collection c)
Appends all of the elements in the specified Collection to the end of this 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.
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 (the item at index 0) of this vector.
Object  get(int index)
Returns the element at the specified position in 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.
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.
void  removeRange(int fromIndex, int toIndex)
Removes from this Vector all of the elements whose index is between fromIndex, inclusive and toIndex, exclusive.
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.
Object[]  toArray()
Returns an array containing all of the elements in this Vector in the correct order.
void  trimToSize()
Trims the capacity of this vector to be the vector's current size.
 
Methods inherited from class java.util.AbstractList
 add, add, addAll, equals, get, hashCode, indexOf, indexOf, iterator, lastIndexOf, lastIndexOf, listIterator, listIterator, remove, removeRange, set
 
Methods inherited from class java.util.AbstractCollection
 add, addAll, clear, contains, containsAll, isEmpty, iterator, remove, removeAll, retainAll, size, toArray, toArray, toString
 
Methods inherited from class java.lang.Object
 clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, 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.

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.
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.

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.
Implements:
size in interface List
Returns:
the number of components in this vector.
Overrides:
size in class AbstractCollection

isEmpty

public boolean isEmpty()
Tests if this vector has no components.
Implements:
isEmpty in interface List
Returns:
true if and only if this vector has no components, that is, its size is zero; false otherwise.
Overrides:
isEmpty in class AbstractCollection

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.
Implements:
contains in interface List
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.
Overrides:
contains in class AbstractCollection

indexOf

public int indexOf(Object elem)
Searches for the first occurence of the given argument, testing for equality using the equals method.
Implements:
indexOf in interface List
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.
Overrides:
indexOf in class AbstractList
See Also:
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.
Implements:
indexOf in interface List
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.
Overrides:
indexOf in class AbstractList
See Also:
equals(Object)

lastIndexOf

public int lastIndexOf(Object elem)
Returns the index of the last occurrence of the specified object in this vector.
Implements:
lastIndexOf in interface List
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.
Overrides:
lastIndexOf in class AbstractList

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.
Implements:
lastIndexOf in interface List
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.
Overrides:
lastIndexOf in class AbstractList

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

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.

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(Object, int), 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:
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.
Returns:
a clone of this vector.
Overrides:
clone in class Object

toArray

public Object[] toArray()
Returns an array containing all of the elements in this Vector in the correct order.
Implements:
toArray in interface List
Overrides:
toArray in class AbstractCollection

get

public Object get(int index)
Returns the element at the specified position in this Vector.
Implements:
get in interface List
Parameters:
index - index of element to return.
Throws:
ArrayIndexOutOfBoundsException - index is out of range (index < 0 || index >= size()).
Overrides:
get in class AbstractList

set

public Object set(int index,
                  Object element)
Replaces the element at the specified position in this Vector with the specified element.
Implements:
set in interface List
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.
Overrides:
set in class AbstractList

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).
Implements:
add in interface List
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()).
Overrides:
add in class AbstractList

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.
Implements:
remove in interface List
Parameters:
index - the index of the element to removed.
Throws:
ArrayIndexOutOfBoundsException - index out of range (index < 0 || index >= size()).
Overrides:
remove in class AbstractList

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).
Implements:
clear in interface List
Throws:
UnsupportedOperationException - clear is not supported by this Set.
Overrides:
clear in class AbstractCollection

addAll

public boolean addAll(Collection c)
Appends all of the elements in the specified Collection to the end of this 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 the specified Collection is this Vector, and this Vector is nonempty.)
Implements:
addAll in interface List
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()).
Overrides:
addAll in class AbstractCollection

removeRange

public void removeRange(int fromIndex,
                        int toIndex)
Removes from this Vector 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 Vector by (toIndex - fromIndex) elements. (If toIndex==fromIndex, this operation has no effect.)
Implements:
removeRange in interface List
Parameters:
fromIndex - index of first element to be removed.
fromIndex - index after last element to be removed.
Throws:
ArrayIndexOutOfBoundsException - fromIndex or toIndex out of range (fromIndex < 0 || fromIndex >= size() || toIndex > size() || toIndex < fromIndex).
Overrides:
removeRange in class AbstractList

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.
Implements:
addAll in interface List
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()).
Overrides:
addAll in class AbstractList

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