java.util
public class Vector<E> extends AbstractList<E> implements List<E>, RandomAccess, Cloneable, Serializable
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.
Since: JDK1.0
Version: 1.94, 06/22/03
See Also: Collection List ArrayList LinkedList
| 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. |
| 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<? extends E> c)
Constructs a vector containing the elements of the specified
collection, in the order they are returned by the collection's
iterator.
| |
| Method Summary | |
|---|---|
| boolean | add(E o)
Appends the specified element to the end of this Vector.
|
| void | add(int index, E element)
Inserts the specified element at the specified position in this Vector.
|
| boolean | addAll(Collection<? extends E> 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<? extends E> c)
Inserts all of the elements in in the specified Collection into this
Vector at the specified position. |
| void | addElement(E 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. |
| E | elementAt(int index)
Returns the component at the specified index. |
| Enumeration<E> | 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. |
| E | firstElement()
Returns the first component (the item at index 0) of
this vector.
|
| E | 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(E 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.
|
| E | 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.
|
| 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. |
| E | remove(int index)
Removes the element at the specified position in this Vector.
|
| 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. |
| E | set(int index, E element)
Replaces the element at the specified position in this Vector with the
specified element.
|
| void | setElementAt(E 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<E> | 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.
|
| <T> T[] | toArray(T[] 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. |
| 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. |
Serial:
Serial:
Any array elements following the last element in the Vector are null.
Serial:
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
Parameters: initialCapacity the initial capacity of the vector.
Throws: IllegalArgumentException if the specified initial capacity is negative
Parameters: c the collection whose elements are to be placed into this vector.
Throws: NullPointerException if the specified collection is null.
Since: 1.2
Parameters: o element to be appended to this Vector.
Returns: true (as per the general contract of Collection.add).
Since: 1.2
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: 1.2
Parameters: c elements to be inserted into this Vector.
Returns: true if this Vector changed as a result of the call.
Throws: NullPointerException if the specified collection is null.
Since: 1.2
Parameters: index index at which to insert first element from the specified collection. c elements to be inserted into this Vector.
Returns: true if this Vector changed as a result of the call.
Throws: ArrayIndexOutOfBoundsException index out of range (index < 0 || index > size()). NullPointerException if the specified collection is null.
Since: 1.2
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.
Returns: the current capacity (the length of its internal data array, kept in the field elementData of this vector).
Since: 1.2
Returns: a clone of this vector.
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.
Parameters: c a collection whose elements will be tested for containment in this Vector
Returns: true if this Vector contains all of the elements in the specified collection.
Throws: NullPointerException if the specified collection is null.
Parameters: anArray the array into which the components get copied.
Throws: NullPointerException if the given array is null.
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.
Returns: an enumeration of the components of this vector.
See Also: Enumeration Iterator
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.
Parameters: minCapacity the desired minimum capacity.
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.
Parameters: o the Object to be compared for equality with this Vector.
Returns: true if the specified Object is equal to this Vector
Returns: the first component of this vector.
Throws: NoSuchElementException if this vector has no components.
Parameters: index index of element to return.
Returns: object at the specified index
Throws: ArrayIndexOutOfBoundsException index is out of range (index < 0 || index >= size()).
Since: 1.2
equals method.
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: equals
index, and testing for equality using
the equals method.
Parameters: elem an object. index the non-negative 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. (Returns -1 if index >= the
current size of this Vector.)
Throws: IndexOutOfBoundsException if index is negative.
See Also: equals
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.
Returns: true if and only if this vector has
no components, that is, its size is zero;
false otherwise.
Returns: the last component of the vector, i.e., the component at index
size() - 1.
Throws: NoSuchElementException if this vector is empty.
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.
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 or equal to 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.)
Throws: IndexOutOfBoundsException if index is greater than or equal to the current size of this vector.
(o==null ? get(i)==null : o.equals(get(i))) (if such
an element exists).
Parameters: o element to be removed from this Vector, if present.
Returns: true if the Vector contained the specified element.
Since: 1.2
Parameters: index the index of the element to removed.
Returns: element that was removed
Throws: ArrayIndexOutOfBoundsException index out of range (index < 0 || index >= size()).
Since: 1.2
Parameters: c a collection of elements to be removed from the Vector
Returns: true if this Vector changed as a result of the call.
Throws: NullPointerException if the specified collection is null.
Since: 1.2
This method is identical in functionality to the clear method (which is part of the List interface).
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.
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.
Parameters: fromIndex index of first element to be removed. toIndex index after last element to be removed.
Parameters: c a collection of elements to be retained in this Vector (all other elements are removed)
Returns: true if this Vector changed as a result of the call.
Throws: NullPointerException if the specified collection is null.
Since: 1.2
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()).
Since: 1.2
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.
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.
Returns: the number of components in this vector.
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.)
Parameters: fromIndex low endpoint (inclusive) of the subList. toIndex 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)
Since: 1.2
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.
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. NullPointerException if the given array is null.
Since: 1.2