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.
| Field Detail |
protected java.lang.Object[] elementData
Any array elements following the last element in the Vector are null.
protected int elementCount
protected int capacityIncrement
private static final long serialVersionUID
| Constructor Detail |
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 negativepublic Vector(int initialCapacity)
initialCapacity - the initial capacity of the vector.IllegalArgumentException - if the specified initial capacity is negativepublic Vector()
public Vector(java.util.Collection c)
c - the collection whose elements are to be placed into this vector.NullPointerException - if the specified collection is null.| Method Detail |
public synchronized void copyInto(java.lang.Object[] anArray)
anArray - the array into which the components get copied.NullPointerException - if the given array is null.public synchronized void trimToSize()
public synchronized 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.private void ensureCapacityHelper(int minCapacity)
public synchronized 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 synchronized int capacity()
public synchronized int size()
public synchronized boolean isEmpty()
true if and only if this vector has no components, that is, its size is zero; false otherwise.public java.util.Enumeration elements()
public boolean contains(java.lang.Object elem)
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(java.lang.Object elem)
equals method.elem - an object.-1 if the object is not found.
public synchronized int indexOf(java.lang.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.public synchronized int lastIndexOf(java.lang.Object elem)
elem - the desired component.-1 if the object is not found.
public synchronized int lastIndexOf(java.lang.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 synchronized java.lang.Object 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.public synchronized java.lang.Object firstElement()
NoSuchElementException - if this vector has no components.public synchronized java.lang.Object lastElement()
size() - 1.NoSuchElementException - if this vector is empty.
public synchronized void setElementAt(java.lang.Object 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.public synchronized 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.
public synchronized void insertElementAt(java.lang.Object 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.public synchronized void addElement(java.lang.Object 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.public synchronized boolean removeElement(java.lang.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.public synchronized void removeAllElements()
This method is identical in functionality to the clear method (which is part of the List interface).
public synchronized java.lang.Object clone()
public synchronized java.lang.Object[] toArray()
public synchronized java.lang.Object[] toArray(java.lang.Object[] 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.
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.NullPointerException - if the given array is null.ArrayStoreException - the runtime type of a is not a supertype of the runtime type of every element in this Vector.public synchronized java.lang.Object get(int index)
index - index of element to return.ArrayIndexOutOfBoundsException - index is out of range (index < 0 || index >= size()).
public synchronized java.lang.Object set(int index,
java.lang.Object element)
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 synchronized boolean add(java.lang.Object o)
o - element to be appended to this Vector.public boolean remove(java.lang.Object o)
(o==null ? get(i)==null : o.equals(get(i))) (if such an element exists).o - element to be removed from this Vector, if present.
public void add(int index,
java.lang.Object element)
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 synchronized java.lang.Object remove(int index)
index - the index of the element to removed.ArrayIndexOutOfBoundsException - index out of range (index < 0 || index >= size()).public void clear()
public synchronized boolean containsAll(java.util.Collection c)
c - a collection whose elements will be tested for containment in this VectorNullPointerException - if the specified collection is null.public synchronized boolean addAll(java.util.Collection c)
c - elements to be inserted into this Vector.NullPointerException - if the specified collection is null.public synchronized boolean removeAll(java.util.Collection c)
c - a collection of elements to be removed from the VectorNullPointerException - if the specified collection is null.public synchronized boolean retainAll(java.util.Collection c)
c - a collection of elements to be retained in this Vector (all other elements are removed)NullPointerException - if the specified collection is null.
public synchronized boolean addAll(int index,
java.util.Collection c)
index - index at which to insert first element from the specified collection.c - elements to be inserted into this Vector.NullPointerException - if the specified collection is null.ArrayIndexOutOfBoundsException - index out of range (index < 0 || index > size()).public synchronized boolean equals(java.lang.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.o - the Object to be compared for equality with this Vector.public synchronized int hashCode()
public synchronized java.lang.String toString()
public synchronized java.util.List 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.)
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)
fromIndex - index of first element to be removed.toIndex - index after last element to be removed.private synchronized void writeObject(java.io.ObjectOutputStream s)