java.lang.Object
java.util.AbstractCollection<E>
java.util.AbstractList<E>
java.util.Vector<E>
public class Vector<E>
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 the Java 2 platform v1.2, 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.
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.
This class is a member of the Java Collections Framework.
Collection, List, ArrayList, LinkedList, Serialized Form
protected int capacityIncrement
protected int elementCount
protected Object[] elementData
Vector()
Vector(Collection<? extends E> c)
Vector(int initialCapacity)
Vector(int initialCapacity, int capacityIncrement)
boolean add(E o)
void add(int index, E element)
boolean addAll(Collection<? extends E> c)
boolean addAll(int index, Collection<? extends E> c)
void addElement(E obj)
int capacity()
void clear()
Object clone()
boolean contains(Object elem)
boolean containsAll(Collection<?> c)
void copyInto(Object[] anArray)
E elementAt(int index)
Enumeration<E> elements()
void ensureCapacity(int minCapacity)
boolean equals(Object o)
E firstElement()
E get(int index)
int hashCode()
int indexOf(Object elem)
equals method. int indexOf(Object elem, int index)
index, and testing for equality using the equals method. void insertElementAt(E obj, int index)
index. boolean isEmpty()
E lastElement()
int lastIndexOf(Object elem)
int lastIndexOf(Object elem, int index)
E remove(int index)
boolean remove(Object o)
boolean removeAll(Collection<?> c)
void removeAllElements()
boolean removeElement(Object obj)
void removeElementAt(int index)
protected void removeRange(int fromIndex, int toIndex)
boolean retainAll(Collection<?> c)
E set(int index, E element)
void setElementAt(E obj, int index)
index of this vector to be the specified object. void setSize(int newSize)
int size()
List<E> subList(int fromIndex, int toIndex)
Object[] toArray()
<T> T[] toArray(T[] a)
String toString()
void trimToSize()
protected Object[] elementData
Any array elements following the last element in the Vector are null.
protected int elementCount
protected int capacityIncrement
public Vector(int initialCapacity,
int capacityIncrement)
initialCapacity - the initial capacity of the vector.
capacityIncrement - the amount by which the capacity is increased when the vector overflows.
IllegalArgumentException - if the specified initial capacity is negative
public Vector(int initialCapacity)
initialCapacity - the initial capacity of the vector.
IllegalArgumentException - if the specified initial capacity is negative
public Vector()
public Vector(Collection<? extends E> c)
c - the collection whose elements are to be placed into this vector.
NullPointerException - if the specified collection is null.
public void copyInto(Object[] anArray)
anArray - the array into which the components get copied.
NullPointerException - if the given array is null.
public void trimToSize()
public void ensureCapacity(int minCapacity)
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 void setSize(int newSize)
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.
ArrayIndexOutOfBoundsException - if new size is negative.
public int capacity()
public int size()
size in interface Collection<E>
size in interface List<E>
size in class AbstractCollection<E>
public boolean isEmpty()
isEmpty in interface Collection<E>
isEmpty in interface List<E>
isEmpty in class AbstractCollection<E>
true if and only if this vector has no components, that is, its size is zero; false otherwise.
public Enumeration<E> elements()
Enumeration, Iterator
public boolean contains(Object elem)
contains in interface Collection<E>
contains in interface List<E>
contains in class AbstractCollection<E>
elem - an object.
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.
public int indexOf(Object elem)
equals method.
indexOf in interface List<E>
indexOf in class AbstractList<E>
elem - an object.
-1 if the object is not found.
Object.equals(Object)
public int indexOf(Object elem,
int index)
index, and testing for equality using the equals method.
elem - an object.
index - the non-negative index to start searching from.
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. (Returns -1 if index >= the current size of this Vector.)
IndexOutOfBoundsException - if index is negative.
Object.equals(Object)
public int lastIndexOf(Object elem)
lastIndexOf in interface List<E>
lastIndexOf in class AbstractList<E>
elem - the desired component.
-1 if the object is not found.
public int lastIndexOf(Object elem,
int index)
elem - the desired component.
index - the index to start searching from.
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. (Returns -1 if index is negative.)
IndexOutOfBoundsException - if index is greater than or equal to the current size of this vector.
public E elementAt(int index)
This method is identical in functionality to the get method (which is part of the List interface).
index - an index into this vector.
ArrayIndexOutOfBoundsException - if the index is negative or not less than the current size of this Vector object. given.
get(int), List
public E firstElement()
NoSuchElementException - if this vector has no components.
public E lastElement()
size() - 1.
NoSuchElementException - if this vector is empty.
public void setElementAt(E obj,
int index)
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.
obj - what the component is to be set to.
index - the specified index.
ArrayIndexOutOfBoundsException - if the index was invalid.
size(), List, set(int, java.lang.Object)
public void removeElementAt(int index)
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.
index - the index of the object to remove.
ArrayIndexOutOfBoundsException - if the index was invalid.
size(), remove(int), List
public void insertElementAt(E obj,
int index)
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.
obj - the component to insert.
index - where to insert the new component.
ArrayIndexOutOfBoundsException - if the index was invalid.
size(), add(int, Object), List
public void addElement(E obj)
This method is identical in functionality to the add(Object) method (which is part of the List interface).
obj - the component to be added.
add(Object), List
public boolean removeElement(Object obj)
This method is identical in functionality to the remove(Object) method (which is part of the List interface).
obj - the component to be removed.
true if the argument was a component of this vector; false otherwise.
List.remove(Object), List
public void removeAllElements()
This method is identical in functionality to the clear method (which is part of the List interface).
clear(), List
public Object clone()
clone in class Object
Cloneable
public Object[] toArray()
toArray in interface Collection<E>
toArray in interface List<E>
toArray in class AbstractCollection<E>
Arrays.asList(Object[])
public <T> T[] toArray(T[] a)
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.
toArray in interface Collection<E>
toArray in interface List<E>
toArray in class AbstractCollection<E>
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.
ArrayStoreException - the runtime type of a is not a supertype of the runtime type of every element in this Vector.
NullPointerException - if the given array is null.
public E get(int index)
get in interface List<E>
get in class AbstractList<E>
index - index of element to return.
ArrayIndexOutOfBoundsException - index is out of range (index < 0 || index >= size()).
public E set(int index,
E element)
set in interface List<E>
set in class AbstractList<E>
index - index of element to replace.
element - element to be stored at the specified position.
ArrayIndexOutOfBoundsException - index out of range (index < 0 || index >= size()).
public boolean add(E o)
add in interface Collection<E>
add in interface List<E>
add in class AbstractList<E>
o - element to be appended to this Vector.
public boolean remove(Object o)
(o==null ? get(i)==null : o.equals(get(i))) (if such an element exists).
remove in interface Collection<E>
remove in interface List<E>
remove in class AbstractCollection<E>
o - element to be removed from this Vector, if present.
public void add(int index,
E element)
add in interface List<E>
add in class AbstractList<E>
index - index at which the specified element is to be inserted.
element - element to be inserted.
ArrayIndexOutOfBoundsException - index is out of range (index < 0 || index > size()).
public E remove(int index)
remove in interface List<E>
remove in class AbstractList<E>
index - the index of the element to removed.
ArrayIndexOutOfBoundsException - index out of range (index < 0 || index >= size()).
public void clear()
clear in interface Collection<E>
clear in interface List<E>
clear in class AbstractList<E>
public boolean containsAll(Collection<?> c)
containsAll in interface Collection<E>
containsAll in interface List<E>
containsAll in class AbstractCollection<E>
c - a collection whose elements will be tested for containment in this Vector
NullPointerException - if the specified collection is null.
AbstractCollection.contains(Object)
public boolean addAll(Collection<? extends E> c)
addAll in interface Collection<E>
addAll in interface List<E>
addAll in class AbstractCollection<E>
c - elements to be inserted into this Vector.
NullPointerException - if the specified collection is null.
AbstractCollection.add(Object)
public boolean removeAll(Collection<?> c)
removeAll in interface Collection<E>
removeAll in interface List<E>
removeAll in class AbstractCollection<E>
c - a collection of elements to be removed from the Vector
NullPointerException - if the specified collection is null.
AbstractCollection.remove(Object), AbstractCollection.contains(Object)
public boolean retainAll(Collection<?> c)
retainAll in interface Collection<E>
retainAll in interface List<E>
retainAll in class AbstractCollection<E>
c - a collection of elements to be retained in this Vector (all other elements are removed)
NullPointerException - if the specified collection is null.
AbstractCollection.remove(Object), AbstractCollection.contains(Object)
public boolean addAll(int index,
Collection<? extends E> c)
addAll in interface List<E>
addAll in class AbstractList<E>
index - index at which to insert first element from the specified collection.
c - elements to be inserted into this Vector.
ArrayIndexOutOfBoundsException - index out of range (index < 0 || index > size()).
NullPointerException - if the specified collection is null.
public boolean equals(Object o)
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.
equals in interface Collection<E>
equals in interface List<E>
equals in class AbstractList<E>
o - the Object to be compared for equality with this Vector.
Object.hashCode(), Hashtable
public int hashCode()
hashCode in interface Collection<E>
hashCode in interface List<E>
hashCode in class AbstractList<E>
Object.equals(java.lang.Object), Hashtable
public String toString()
toString in class AbstractCollection<E>
public List<E> subList(int fromIndex,
int toIndex)
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.)
subList in interface List<E>
subList in class AbstractList<E>
fromIndex - low endpoint (inclusive) of the subList.
toIndex - high endpoint (exclusive) of the subList.
IndexOutOfBoundsException - endpoint index value out of range (fromIndex < 0 || toIndex > size)
IllegalArgumentException - endpoint indices out of order (fromIndex > toIndex)
protected void removeRange(int fromIndex,
int toIndex)
removeRange in class AbstractList<E>
fromIndex - index of first element to be removed.
toIndex - index after last element to be removed.
Copyright © 2004, 2010 Oracle and/or its affiliates. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.
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