IdentitySet.java Source code

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Here is the source code for IdentitySet.java

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/*
 * 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();
    }
}