java.util.Vector

public class java.util

Vector<E>

Java SE 6

Extends: AbstractCollection > AbstractList

Implements: List, RandomAccess, Cloneable, Serializable

Extended by: Stack

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.

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.

As of the Java 2 platform v1.2, this class was retrofitted to implement the List interface, making it a member of the Java Collections Framework. Unlike the new collection implementations, Vector is synchronized.

version 1.106, 06/16/06

since JDK1.0

See also java.util.Collection, java.util.List, java.util.ArrayList, java.util.LinkedList

Fields

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.

serial

protected int

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

serial

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.

serial

Constructors

public

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

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

public

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

initialCapacity	the initial capacity of the vector
Throws	IllegalArgumentException: if the specified initial capacity is negative

public

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

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.

c	the collection whose elements are to be placed into this vector
Throws	NullPointerException: if the specified collection is null
since	1.2

Methods

public boolean

add(Object e)
Appends the specified element to the end of this Vector.

e	element to be appended to this Vector
return	`true` (as specified by `Collection#add`)
since	1.2

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).

index	index at which the specified element is to be inserted
element	element to be inserted
Throws	ArrayIndexOutOfBoundsException: if the index is out of range (`index < 0 \|\| index > size()`)
since	1.2

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.)

c	elements to be inserted into this Vector
return	`true` if this Vector changed as a result of the call
Throws	NullPointerException: if the specified collection is null
since	1.2

public boolean

addAll(int index, Collection c)
Inserts all of the elements 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.

index	index at which to insert the first element from the specified collection
c	elements to be inserted into this Vector
return	`true` if this Vector changed as a result of the call
Throws	ArrayIndexOutOfBoundsException: if the index is out of range (`index < 0 \|\| index > size()`)
Throws	NullPointerException: if the specified collection is null
since	1.2

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(E) method (which is part of the List interface).

obj the component to be added

public int

capacity()
Returns the current capacity of this vector.

return the current capacity (the length of its internal data array, kept in the field elementData of this vector)

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).

since

1.2

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.

return

a clone of this vector

public boolean

contains(Object o)
Returns true if this vector contains the specified element. More formally, returns true if and only if this vector contains at least one element e such that (o==null ? e==null : o.equals(e)).

o	element whose presence in this vector is to be tested
return	`true` if this vector contains the specified element

public boolean

containsAll(Collection c)
Returns true if this Vector contains all of the elements in the specified Collection.

c	a collection whose elements will be tested for containment in this Vector
return	true if this Vector contains all of the elements in the specified collection
Throws	NullPointerException: if the specified collection is null

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.

anArray	the array into which the components get copied
Throws	NullPointerException: if the given array is null
Throws	IndexOutOfBoundsException: if the specified array is not large enough to hold all the components of this vector
Throws	ArrayStoreException: if a component of this vector is not of a runtime type that can be stored in the specified array
See also	toArray(Object[])

public Object

elementAt(int index)
Returns the component at the specified index.

This method is identical in functionality to the #get(int) method (which is part of the List interface).

index an index into this vector

return the component at the specified index

Throws ArrayIndexOutOfBoundsException: if the index is out of range (index < 0 || index >= size())

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.

return	an enumeration of the components of this vector
See also	java.util.Iterator

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.

minCapacity the desired minimum capacity

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.

o	the Object to be compared for equality with this Vector
return	true if the specified Object is equal to this Vector

public Object

firstElement()
Returns the first component (the item at index 0) of this vector.

return	the first component of this vector
Throws	NoSuchElementException: if this vector has no components

public Object

get(int index)
Returns the element at the specified position in this Vector.

index	index of the element to return
return	object at the specified index
Throws	ArrayIndexOutOfBoundsException: if the index is out of range (`index < 0 \|\| index >= size()`)
since	1.2

public int

hashCode()
Returns the hash code value for this Vector.

public int

indexOf(Object o)
Returns the index of the first occurrence of the specified element in this vector, or -1 if this vector does not contain the element. More formally, returns the lowest index i such that (o==null ? get(i)==null : o.equals(get(i))), or -1 if there is no such index.

o	element to search for
return	the index of the first occurrence of the specified element in this vector, or -1 if this vector does not contain the element

public int

indexOf(Object o, int index)
Returns the index of the first occurrence of the specified element in this vector, searching forwards from index, or returns -1 if the element is not found. More formally, returns the lowest index i such that (i >= index && (o==null ? get(i)==null : o.equals(get(i)))), or -1 if there is no such index.

o	element to search for
index	index to start searching from
return	the index of the first occurrence of the element in this vector at position `index` or later in the vector; `-1` if the element is not found.
Throws	IndexOutOfBoundsException: if the specified index is negative
See also	equals(Object)

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(int, E) 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.

obj the component to insert

index where to insert the new component

Throws ArrayIndexOutOfBoundsException: if the index is out of range (index < 0 || index > size())

public Object

lastElement()
Returns the last component of the vector.

return	the last component of the vector, i.e., the component at index `size() - 1`.
Throws	NoSuchElementException: if this vector is empty

public int

lastIndexOf(Object o)
Returns the index of the last occurrence of the specified element in this vector, or -1 if this vector does not contain the element. More formally, returns the highest index i such that (o==null ? get(i)==null : o.equals(get(i))), or -1 if there is no such index.

o	element to search for
return	the index of the last occurrence of the specified element in this vector, or -1 if this vector does not contain the element

public int

lastIndexOf(Object o, int index)
Returns the index of the last occurrence of the specified element in this vector, searching backwards from index, or returns -1 if the element is not found. More formally, returns the highest index i such that (i <= index && (o==null ? get(i)==null : o.equals(get(i)))), or -1 if there is no such index.

o	element to search for
index	index to start searching backwards from
return	the index of the last occurrence of the element at position less than or equal to `index` in this vector; -1 if the element is not found.
Throws	IndexOutOfBoundsException: if the specified index is greater than or equal to the current size of this vector

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).

o	element to be removed from this Vector, if present
return	true if the Vector contained the specified element
since	1.2

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.

Throws	ArrayIndexOutOfBoundsException: if the index is out of range (`index < 0 \|\| index >= size()`)
index	the index of the element to be removed
return	element that was removed
since	1.2

public boolean

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

c	a collection of elements to be removed from the Vector
return	true if this Vector changed as a result of the call
Throws	ClassCastException: if the types of one or more elements in this vector are incompatible with the specified collection (optional)
Throws	NullPointerException: if this vector contains one or more null elements and the specified collection does not support null elements (optional), or if the specified collection is null
since	1.2

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).

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).

obj the component to be removed

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

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(int) method (which is part of the List interface). Note that the remove method returns the old value that was stored at the specified position.

index the index of the object to remove

Throws ArrayIndexOutOfBoundsException: if the index is out of range (index < 0 || index >= size())

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.)

fromIndex	index of first element to be removed
toIndex	index after last element to be removed

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.

c	a collection of elements to be retained in this Vector (all other elements are removed)
return	true if this Vector changed as a result of the call
Throws	ClassCastException: if the types of one or more elements in this vector are incompatible with the specified collection (optional)
Throws	NullPointerException: if this vector contains one or more null elements and the specified collection does not support null elements (optional), or if the specified collection is null
since	1.2

public Object

set(int index, Object element)
Replaces the element at the specified position in this Vector with the specified element.

index	index of the element to replace
element	element to be stored at the specified position
return	the element previously at the specified position
Throws	ArrayIndexOutOfBoundsException: if the index is out of range (`index < 0 \|\| index >= size()`)
since	1.2

public int

size()
Returns the number of components in this vector.

return

the number of components in this vector

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.)

fromIndex low endpoint (inclusive) of the subList

toIndex high endpoint (exclusive) of the subList

return a view of the specified range within this List

Throws IndexOutOfBoundsException: if an endpoint index value is out of range (fromIndex < 0 || toIndex > size)

Throws IllegalArgumentException: if the endpoint indices are out of order (fromIndex > toIndex)

public Object[]

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

since

1.2

public Object[]<T>

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.)

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.

return an array containing the elements of the Vector

Throws ArrayStoreException: if the runtime type of a is not a supertype of the runtime type of every element in this Vector

Throws NullPointerException: if the given array is null

since 1.2

public String

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

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.

Properties

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(int, E) 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.

obj what the component is to be set to

index the specified index

Throws ArrayIndexOutOfBoundsException: if the index is out of range (index < 0 || index >= size())

public boolean

isEmpty()
Tests if this vector has no components.

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

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.

newSize	the new size of this vector
Throws	ArrayIndexOutOfBoundsException: if the new size is negative

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Java SE 6

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