public class

IdentitySet

extends Object
implements Iterable<T> 
// IdentitySet.java

/**
 *      Copyright (C) 2008 10gen Inc.
 *  
 *   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.
 */

package com.mongodb.util;

import java.util.Collection;
import java.util.IdentityHashMap;
import java.util.Iterator;

public class IdentitySet<T> implements Iterable<T> {

    public IdentitySet(){
    }

    public IdentitySet( Iterable<T> copy ){
        for ( T t : copy )
            add( t );
    }

    public boolean add( T t ){
        return _map.put( t , "a" ) == null;
    }

    public boolean contains( T t ){
        return _map.containsKey( t );
    }

    public void remove( T t ){
        _map.remove( t );
    }

    public void removeall( Iterable<T> coll ){
        for ( T t : coll )
            _map.remove( t );
    }

    public void clear(){
	_map.clear();
    }

    public int size(){
	return _map.size();
    }

    public Iterator<T> iterator(){
        return _map.keySet().iterator();
    }

    public void addAll( Collection<T> c ){
        for ( T t : c ){
            add( t );
        }
    }

    public void addAll( IdentitySet<T> c ){
        for ( T t : c )
            add( t );
    }

    public void removeAll( Iterable<T> prev ){
        for ( T t : prev )
            remove( t );
    }

    final IdentityHashMap<T,String> _map = new IdentityHashMap<T,String>();
}