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java.util
class AbstractCollection

java.lang.Object extended by java.util.AbstractCollection
All Implemented Interfaces:
Collection
Direct Known Subclasses:
AbstractList, AbstractQueue, AbstractSet, ArrayDeque

public abstract class AbstractCollection
extends Object
implements Collection

This class provides a skeletal implementation of the Collection interface, to minimize the effort required to implement this interface.

To implement an unmodifiable collection, the programmer needs only to extend this class and provide implementations for the iterator and size methods. (The iterator returned by the iterator method must implement hasNext and next.)

To implement a modifiable collection, the programmer must additionally override this class's add method (which otherwise throws an UnsupportedOperationException), and the iterator returned by the iterator method must additionally implement its remove method.

The programmer should generally provide a void (no argument) and Collection constructor, as per the recommendation in the Collection interface specification.

The documentation for each non-abstract method in this class describes its implementation in detail. Each of these methods may be overridden if the collection being implemented admits a more efficient implementation.

This class is a member of the Java Collections Framework.


Constructor Summary
protected

          Sole constructor.
 
Method Summary
 boolean

          
 boolean

          
 void

          
 boolean

          
 boolean

          
 boolean

          
abstract Iterator

          Returns an iterator over the elements contained in this collection.
 boolean

          
 boolean

          
 boolean

          
abstract int

          
 Object[]

          
 Object[]

          
 String

          Returns a string representation of this collection.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

AbstractCollection

protected AbstractCollection()
Sole constructor. (For invocation by subclass constructors, typically implicit.)

Method Detail

add

public boolean add(Object e)
{@inheritDoc}

This implementation always throws an UnsupportedOperationException.

Parameters:
e

addAll

public boolean addAll(Collection c)
{@inheritDoc}

This implementation iterates over the specified collection, and adds each object returned by the iterator to this collection, in turn.

Note that this implementation will throw an UnsupportedOperationException unless add is overridden (assuming the specified collection is non-empty).

Parameters:
c

clear

public void clear()
{@inheritDoc}

This implementation iterates over this collection, removing each element using the Iterator.remove operation. Most implementations will probably choose to override this method for efficiency.

Note that this implementation will throw an UnsupportedOperationException if the iterator returned by this collection's iterator method does not implement the remove method and this collection is non-empty.


contains

public boolean contains(Object o)
{@inheritDoc}

This implementation iterates over the elements in the collection, checking each element in turn for equality with the specified element.

Parameters:
o

containsAll

public boolean containsAll(Collection c)
{@inheritDoc}

This implementation iterates over the specified collection, checking each element returned by the iterator in turn to see if it's contained in this collection. If all elements are so contained true is returned, otherwise false.

Parameters:
c

isEmpty

public boolean isEmpty()
{@inheritDoc}

This implementation returns size() == 0.


iterator

public abstract Iterator iterator()
Returns an iterator over the elements contained in this collection.

Returns:
an iterator over the elements contained in this collection

remove

public boolean remove(Object o)
{@inheritDoc}

This implementation iterates over the collection looking for the specified element. If it finds the element, it removes the element from the collection using the iterator's remove method.

Note that this implementation throws an UnsupportedOperationException if the iterator returned by this collection's iterator method does not implement the remove method and this collection contains the specified object.

Parameters:
o

removeAll

public boolean removeAll(Collection c)
{@inheritDoc}

This implementation iterates over this collection, checking each element returned by the iterator in turn to see if it's contained in the specified collection. If it's so contained, it's removed from this collection with the iterator's remove method.

Note that this implementation will throw an UnsupportedOperationException if the iterator returned by the iterator method does not implement the remove method and this collection contains one or more elements in common with the specified collection.

Parameters:
c

retainAll

public boolean retainAll(Collection c)
{@inheritDoc}

This implementation iterates over this collection, checking each element returned by the iterator in turn to see if it's contained in the specified collection. If it's not so contained, it's removed from this collection with the iterator's remove method.

Note that this implementation will throw an UnsupportedOperationException if the iterator returned by the iterator method does not implement the remove method and this collection contains one or more elements not present in the specified collection.

Parameters:
c

size

public abstract int size()

toArray

public Object[] toArray()
{@inheritDoc}

This implementation returns an array containing all the elements returned by this collection's iterator, in the same order, stored in consecutive elements of the array, starting with index {@code 0}. The length of the returned array is equal to the number of elements returned by the iterator, even if the size of this collection changes during iteration, as might happen if the collection permits concurrent modification during iteration. The {@code size} method is called only as an optimization hint; the correct result is returned even if the iterator returns a different number of elements.

This method is equivalent to:

 {@code
 List list = new ArrayList(size());
 for (E e : this)
     list.add(e);
 return list.toArray();
 }


toArray

public Object[] toArray(Object[] a)
{@inheritDoc}

This implementation returns an array containing all the elements returned by this collection's iterator in the same order, stored in consecutive elements of the array, starting with index {@code 0}. If the number of elements returned by the iterator is too large to fit into the specified array, then the elements are returned in a newly allocated array with length equal to the number of elements returned by the iterator, even if the size of this collection changes during iteration, as might happen if the collection permits concurrent modification during iteration. The {@code size} method is called only as an optimization hint; the correct result is returned even if the iterator returns a different number of elements.

This method is equivalent to:

 {@code
 List list = new ArrayList(size());
 for (E e : this)
     list.add(e);
 return list.toArray(a);
 }

Parameters:
a

toString

public String toString()
Returns a string representation of this collection. The string representation consists of a list of the collection's elements in the order they are returned by its iterator, enclosed in square brackets ("[]"). Adjacent elements are separated by the characters ", " (comma and space). Elements are converted to strings as by {@link String#valueOf(Object)}.

Overrides:
toString in class Object
Returns:
a string representation of this collection


This documentation differs from the official API. Jadeite adds extra features to the API including: variable font sizes, constructions examples, placeholders for classes and methods, and auto-generated “See Also” links. Additionally it is missing some items found in standard Javadoc documentation, including: generics type information, “Deprecated” tags and comments, “See Also” links, along with other minor differences. Please send any questions or feedback to bam@cs.cmu.edu.
This page displays the Jadeite version of the documention, which is derived from the offical documentation that contains this copyright notice:
Copyright 2008 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.
The official Sun™ documentation can be found here at http://java.sun.com/javase/6/docs/api/.