Mega Code Archive
Set implementation that use == instead of equals()
<![CDATA[
/*
* Hibernate, Relational Persistence for Idiomatic Java
*
* Copyright (c) 2008, Red Hat Middleware LLC or third-party contributors as
* indicated by the @author tags or express copyright attribution
* statements applied by the authors. All third-party contributions are
* distributed under license by Red Hat Middleware LLC.
*
* This copyrighted material is made available to anyone wishing to use, modify,
* copy, or redistribute it subject to the terms and conditions of the GNU
* Lesser General Public License, as published by the Free Software Foundation.
*
* This program 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 Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this distribution; if not, write to:
* Free Software Foundation, Inc.
* 51 Franklin Street, Fifth Floor
* Boston, MA 02110-1301 USA
*
*/
import java.util.Collection;
import java.util.IdentityHashMap;
import java.util.Iterator;
import java.util.Set;
/**
* Set implementation that use == instead of equals() as its comparison
* mechanism. This is achieved by internally using an IdentityHashMap.
*
* @author Emmanuel Bernard
*/
public class IdentitySet implements Set {
private static final Object DUMP_VALUE = new Object();
private final IdentityHashMap map;
/**
* Create an IdentitySet with default sizing.
*/
public IdentitySet() {
this.map = new IdentityHashMap();
}
/**
* Create an IdentitySet with the given sizing.
*
* @param sizing The sizing of the set to create.
*/
public IdentitySet(int sizing) {
this.map = new IdentityHashMap( sizing );
}
public int size() {
return map.size();
}
public boolean isEmpty() {
return map.isEmpty();
}
public boolean contains(Object o) {
return map.get( o ) == DUMP_VALUE;
}
public Iterator iterator() {
return map.entrySet().iterator();
}
public Object[] toArray() {
return map.entrySet().toArray();
}
public Object[] toArray(Object[] a) {
return map.entrySet().toArray( a );
}
public boolean add(Object o) {
return map.put( o, DUMP_VALUE ) == null;
}
public boolean remove(Object o) {
return map.remove( o ) == DUMP_VALUE;
}
public boolean containsAll(Collection c) {
Iterator it = c.iterator();
while ( it.hasNext() ) {
if ( !map.containsKey( it.next() ) ) {
return false;
}
}
return true;
}
public boolean addAll(Collection c) {
Iterator it = c.iterator();
boolean changed = false;
while ( it.hasNext() ) {
if ( this.add( it.next() ) ) {
changed = true;
}
}
return changed;
}
public boolean retainAll(Collection c) {
//doable if needed
throw new UnsupportedOperationException();
}
public boolean removeAll(Collection c) {
Iterator it = c.iterator();
boolean changed = false;
while ( it.hasNext() ) {
if ( this.remove( it.next() ) ) {
changed = true;
}
}
return changed;
}
public void clear() {
map.clear();
}
}
]]>