identityset.java

一个Java持久层类库

//$Id: IdentitySet.java 8807 2005-12-09 15:27:05Z epbernard $
package org.hibernate.util;

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();
	}
}