java.util

Class AbstractSet<E>

Implemented Interfaces:
Collection<E>, Iterable<E>, Set<E>
Known Direct Subclasses:
ConcurrentSkipListSet<E>, CopyOnWriteArraySet<E>, EnumSet<T,extends,Enum,T>, HashSet<T>, TreeSet<T>

public abstract class AbstractSet<E>
extends AbstractCollection<E>
implements Set<E>

An abstract implementation of Set to make it easier to create your own implementations. In order to create a Set, subclass AbstractSet and implement the same methods that are required for AbstractCollection (although these methods must of course meet the requirements that Set puts on them - specifically, no element may be in the set more than once). This class simply provides implementations of equals() and hashCode() to fulfil the requirements placed on them by the Set interface.
Since:
1.2
See Also:
Collection, AbstractCollection, Set, HashSet, TreeSet, LinkedHashSet

Constructor Summary

AbstractSet()
The main constructor, for use by subclasses.

Method Summary

boolean
equals(Object o)
Tests whether the given object is equal to this Set.
int
hashCode()
Returns a hash code for this Set.
boolean
removeAll(Collection c)
Removes from this set all elements in the given collection (optional operation).

Methods inherited from class java.util.AbstractCollection<E>

T[] toArray, add, addAll, clear, contains, containsAll, isEmpty, iterator, remove, removeAll, retainAll, size, toArray, toString

Methods inherited from class java.lang.Object

clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

AbstractSet

protected AbstractSet()
The main constructor, for use by subclasses.

Method Details

equals

public boolean equals(Object o)
Tests whether the given object is equal to this Set. This implementation first checks whether this set is the given object, and returns true if so. Otherwise, if o is a Set and is the same size as this one, it returns the result of calling containsAll on the given Set. Otherwise, it returns false.
Specified by:
equals in interface Set<E>
equals in interface Collection<E>
Overrides:
equals in interface Object
Parameters:
o - the Object to be tested for equality with this Set
Returns:
true if the given object is equal to this Set

hashCode

public int hashCode()
Returns a hash code for this Set. The hash code of a Set is the sum of the hash codes of all its elements, except that the hash code of null is defined to be zero. This implementation obtains an Iterator over the Set, and sums the results.
Specified by:
hashCode in interface Set<E>
hashCode in interface Collection<E>
Overrides:
hashCode in interface Object
Returns:
a hash code for this Set

removeAll

public boolean removeAll(Collection c)
Removes from this set all elements in the given collection (optional operation). This implementation uses size() to determine the smaller collection. Then, if this set is smaller, it iterates over the set, calling Iterator.remove if the collection contains the element. If this set is larger, it iterates over the collection, calling Set.remove for all elements in the collection. Note that this operation will fail if a remove methods is not supported.
Specified by:
removeAll in interface Set<E>
removeAll in interface Collection<E>
Overrides:
removeAll in interface AbstractCollection<E>
Parameters:
c - the collection of elements to remove
Returns:
true if the set was modified as a result
Throws:
UnsupportedOperationException - if remove is not supported
NullPointerException - if the collection is null

AbstractSet.java -- Abstract implementation of most of Set Copyright (C) 1998, 2000, 2001, 2004, 2005 Free Software Foundation, Inc. This file is part of GNU Classpath. GNU Classpath is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. GNU Classpath is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GNU Classpath; see the file COPYING. If not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. Linking this library statically or dynamically with other modules is making a combined work based on this library. Thus, the terms and conditions of the GNU General Public License cover the whole combination. As a special exception, the copyright holders of this library give you permission to link this library with independent modules to produce an executable, regardless of the license terms of these independent modules, and to copy and distribute the resulting executable under terms of your choice, provided that you also meet, for each linked independent module, the terms and conditions of the license of that module. An independent module is a module which is not derived from or based on this library. If you modify this library, you may extend this exception to your version of the library, but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version.