Mega Code Archive
Set that compares object by identity rather than equality
<![CDATA[
// $Id: IdentitySet.java 16179 2009-03-18 11:08:10Z hardy.ferentschik $
/*
* JBoss, Home of Professional Open Source
* Copyright 2008, Red Hat Middleware LLC, and individual contributors
* by the @authors tag. See the copyright.txt in the distribution for a
* full listing of individual contributors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* http://www.apache.org/licenses/LICENSE-2.0
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import java.util.Collection;
import java.util.IdentityHashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
/**
* Set that compares object by identity rather than equality. Wraps around a <code>IdentityHashMap</code>
*
* @author Emmanuel Bernard
*/
public class IdentitySet implements Set {
private Map<Object, Object> map;
private Object CONTAINS = new Object();
public IdentitySet() {
this( 10 );
}
public IdentitySet(int size) {
this.map = new IdentityHashMap<Object, Object>( size );
}
public int size() {
return map.size();
}
public boolean isEmpty() {
return map.isEmpty();
}
public boolean contains(Object o) {
return map.containsKey( o );
}
public Iterator iterator() {
return map.keySet().iterator();
}
public Object[] toArray() {
return map.keySet().toArray();
}
public boolean add(Object o) {
return map.put( o, CONTAINS ) == null;
}
public boolean remove(Object o) {
return map.remove( o ) == CONTAINS;
}
public boolean addAll(Collection c) {
boolean doThing = false;
for ( Object o : c ) {
doThing = doThing || add( o );
}
return doThing;
}
public void clear() {
map.clear();
}
public boolean removeAll(Collection c) {
boolean remove = false;
for ( Object o : c ) {
remove = remove || remove( o );
}
return remove;
}
public boolean retainAll(Collection c) {
throw new UnsupportedOperationException();
}
public boolean containsAll(Collection c) {
for ( Object o : c ) {
if ( !contains( o ) ) {
return false;
}
}
return true;
}
public Object[] toArray(Object[] a) {
return map.keySet().toArray( a );
}
@Override
public String toString() {
return "IdentitySet{" +
"map=" + map +
'}';
}
}
]]>