IdentitySet.java Source code

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Here is the source code for IdentitySet.java

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// $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 + '}';
    }
}