Class: java.util.Vector<E>
- public class Vector<E>
- extends AbstractList<E>
- implements List<E>, RandomAccess, 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 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.
Inheritance
Superclass tree:- java.lang.Object
- java.util.AbstractCollection<E>
- java.util.AbstractList<E>
- java.util.Vector
- RandomAccess
- Cloneable
- Serializable
- List<E>
- Collection<E>
- Iterable<E>
Methods
-
Vectortop
public Vector()Constructs an empty vector so that its internal data array has size 10 and its standard capacity increment is zero. -
Vectortop
public Vector(int initialCapacity)Constructs an empty vector with the specified initial capacity and with its capacity increment equal to zero. -
Vectortop
public Vector(int initialCapacity, int capacityIncrement)Constructs an empty vector with the specified initial capacity and capacity increment. -
Vectortop
public 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. -
addtop
public void add(int index, E 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).- Override hierarchy:
- add from AbstractList<E>
-
addtop
public synchronized boolean add(E o)Appends the specified element to the end of this Vector.- Specified by:
- add from List<E>
- add from Collection<E>
- Override hierarchy:
- add from AbstractList<E>
- add from AbstractCollection<E>
-
addAlltop
public synchronized boolean addAll(int index, Collection<? extends E> 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.- Override hierarchy:
- addAll from AbstractList<E>
-
addAlltop
public synchronized 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. 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.)- Specified by:
- addAll from List<E>
- addAll from Collection<E>
- Override hierarchy:
- addAll from AbstractCollection<E>
-
addElementtop
public synchronized void addElement(E 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).
-
capacitytop
public synchronized int capacity()Returns the current capacity of this vector. -
cleartop
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).- Specified by:
- clear from List<E>
- clear from Collection<E>
- Override hierarchy:
- clear from AbstractList<E>
- clear from AbstractCollection<E>
-
clonetop
public synchronized 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. -
containstop
public boolean contains(Object elem)Tests if the specified object is a component in this vector.- Specified by:
- contains from List<E>
- contains from Collection<E>
- Override hierarchy:
- contains from AbstractCollection<E>
-
containsAlltop
public synchronized boolean containsAll(Collection<?> c)Returns true if this Vector contains all of the elements in the specified Collection.- Specified by:
- containsAll from List<E>
- containsAll from Collection<E>
- Override hierarchy:
- containsAll from AbstractCollection<E>
-
copyIntotop
public synchronized 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. -
elementAttop
public synchronized E 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).
-
elementstop
public Enumeration<E> 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. -
ensureCapacitytop
public synchronized 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.
-
ensureCapacityHelpertop
private void ensureCapacityHelper(int minCapacity)This implements the unsynchronized semantics of ensureCapacity. Synchronized methods in this class can internally call this method for ensuring capacity without incurring the cost of an extra synchronization. -
equalstop
public synchronized 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 elementse1ande2are 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.- Specified by:
- equals from List<E>
- equals from Collection<E>
- Override hierarchy:
- equals from AbstractList<E>
- equals from Object
-
firstElementtop
public synchronized E firstElement()Returns the first component (the item at index 0) of this vector. -
gettop
public synchronized E get(int index)Returns the element at the specified position in this Vector.- Override hierarchy:
- get from AbstractList<E>
-
hashCodetop
public synchronized int hashCode()Returns the hash code value for this Vector.- Specified by:
- hashCode from List<E>
- hashCode from Collection<E>
- Override hierarchy:
- hashCode from AbstractList<E>
- hashCode from Object
-
indexOftop
public int indexOf(Object elem)Searches for the first occurence of the given argument, testing for equality using theequalsmethod.- Override hierarchy:
- indexOf from AbstractList<E>
-
indexOftop
public synchronized int indexOf(Object elem, int index)Searches for the first occurence of the given argument, beginning the search atindex, and testing for equality using theequalsmethod. -
insertElementAttop
public synchronized void insertElementAt(E obj, int index)Inserts the specified object as a component in this vector at the specifiedindex. Each component in this vector with an index greater or equal to the specifiedindexis 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
0and 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.
-
isEmptytop
public synchronized boolean isEmpty()Tests if this vector has no components.- Specified by:
- isEmpty from List<E>
- isEmpty from Collection<E>
- Override hierarchy:
- isEmpty from AbstractCollection<E>
-
lastElementtop
public synchronized E lastElement()Returns the last component of the vector. -
lastIndexOftop
public synchronized int lastIndexOf(Object elem)Returns the index of the last occurrence of the specified object in this vector.- Specified by:
- lastIndexOf from List<E>
- Override hierarchy:
- lastIndexOf from AbstractList<E>
-
lastIndexOftop
public synchronized int lastIndexOf(Object elem, int index)Searches backwards for the specified object, starting from the specified index, and returns an index to it. -
removetop
public synchronized E 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.- Override hierarchy:
- remove from AbstractList<E>
-
removetop
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).- Specified by:
- remove from List<E>
- remove from Collection<E>
- Override hierarchy:
- remove from AbstractCollection<E>
-
removeAlltop
public synchronized boolean removeAll(Collection<?> c)Removes from this Vector all of its elements that are contained in the specified Collection.- Specified by:
- removeAll from List<E>
- removeAll from Collection<E>
- Override hierarchy:
- removeAll from AbstractCollection<E>
-
removeAllElementstop
public synchronized 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).
-
removeElementtop
public synchronized 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).
-
removeElementAttop
public synchronized void removeElementAt(int index)Deletes the component at the specified index. Each component in this vector with an index greater or equal to the specifiedindexis 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
0and 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.
-
removeRangetop
synchronized 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.)- Override hierarchy:
- removeRange from AbstractList<E>
-
retainAlltop
public synchronized 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.- Specified by:
- retainAll from List<E>
- retainAll from Collection<E>
- Override hierarchy:
- retainAll from AbstractCollection<E>
-
settop
public synchronized E set(int index, E element)Replaces the element at the specified position in this Vector with the specified element.- Override hierarchy:
- set from AbstractList<E>
-
setElementAttop
public synchronized void setElementAt(E obj, int index)Sets the component at the specifiedindexof 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
0and 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.
-
setSizetop
public synchronized void setSize(int newSize)Sets the size of this vector. If the new size is greater than the current size, newnullitems are added to the end of the vector. If the new size is less than the current size, all components at indexnewSizeand greater are discarded. -
sizetop
public synchronized int size()Returns the number of components in this vector.- Specified by:
- size from List<E>
- size from Collection<E>
- Override hierarchy:
- size from AbstractCollection<E>
-
subListtop
public synchronized List<E> 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.)
- Override hierarchy:
- subList from AbstractList<E>
-
toArraytop
public synchronized Object[] toArray()Returns an array containing all of the elements in this Vector in the correct order.- Specified by:
- toArray from List<E>
- toArray from Collection<E>
- Override hierarchy:
- toArray from AbstractCollection<E>
-
toArraytop
public synchronized <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. 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.
- Specified by:
- toArray from List<E>
- toArray from Collection<E>
- Override hierarchy:
- toArray from AbstractCollection<E>
-
toStringtop
public synchronized String toString()Returns a string representation of this Vector, containing the String representation of each element.- Override hierarchy:
- toString from AbstractCollection<E>
- toString from Object
-
trimToSizetop
public synchronized 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. -
writeObjecttop
synchronized private void writeObject(ObjectOutputStream s) throws IOExceptionSave the state of the Vector instance to a stream (that is, serialize it). This method is present merely for synchronization. It just calls the default readObject method.
Fields
-
capacityIncrement
protected int capacityIncrementThe 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. -
elementCount
protected int elementCountThe number of valid components in this Vector object. Components elementData[0] through elementData[elementCount-1] are the actual items. -
elementData
protected Object[] elementDataThe 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.
-
serialVersionUID
static final private long serialVersionUID = -2767605614048989439use serialVersionUID from JDK 1.0.2 for interoperability