Dépôt officiel du code source de l'ERP OpenConcerto

/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.

 *

 * Copyright 2011-2019 OpenConcerto, by ILM Informatique. All rights reserved.

 *

 * The contents of this file are subject to the terms of the GNU General Public License Version 3

 * only ("GPL"). You may not use this file except in compliance with the License. You can obtain a

 * copy of the License at http://www.gnu.org/licenses/gpl-3.0.html See the License for the specific

 * language governing permissions and limitations under the License.

 *

 * When distributing the software, include this License Header Notice in each file.

 */

 package org.openconcerto.utils.cc;

import java.util.AbstractSet;

import java.util.Collection;

import java.util.IdentityHashMap;

import java.util.Iterator;

/**

 * This class implements the <tt>Set</tt> interface with a hash table, using reference-equality in

 * place of object-equality when comparing items. In other words, in an <tt>IdentityHashSet</tt>,

 * two keys <tt>k1</tt> and <tt>k2</tt> are considered equal if and only if <tt>(k1==k2)</tt>. (In

 * normal <tt>Set</tt> implementations (like <tt>HashSet</tt>) two keys <tt>k1</tt> and <tt>k2</tt>

 * are considered equal if and only if <tt>(k1==null ? k2==null : k1.equals(k2))</tt>.)

 *

 * @param <E> the type of elements maintained by this set

 */

public final class IdentityHashSet<E> extends AbstractSet<E> implements IdentitySet<E>, Cloneable {

    static private final Object VALUE = new Object();

    private final IdentityHashMap<E, Object> map;

    public IdentityHashSet() {

        this.map = new IdentityHashMap<E, Object>();

    }

    public IdentityHashSet(int expectedMaxSize) {

        this.map = new IdentityHashMap<E, Object>(expectedMaxSize);

    }

    public IdentityHashSet(Collection<? extends E> c) {

        this.map = new IdentityHashMap<E, Object>(Math.max((int) (c.size() / .75f) + 1, 16));

        this.addAll(c);

    }

    @Override

    public boolean add(E e) {

        return this.map.put(e, VALUE) != VALUE;

    }

    @Override

    public boolean addAll(Collection<? extends E> c) {

        // let the super which calls add() since we don't want to build a map to use Map.addAll()

        return super.addAll(c);

    }

    @Override

    public void clear() {

        this.map.clear();

    }

    @Override

    public int size() {

        return this.map.size();

    }

    @Override

    public boolean isEmpty() {

        return this.map.isEmpty();

    }

    @Override

    public Iterator<E> iterator() {

        return this.map.keySet().iterator();

    }

    @Override

    public boolean contains(Object o) {

        return this.map.containsKey(o);

    }

    @Override

    public boolean containsAll(Collection<?> c) {

        return this.map.keySet().containsAll(c);

    }

    @Override

    public boolean remove(Object o) {

        return this.map.remove(o) == VALUE;

    }

    @Override

    public boolean removeAll(Collection<?> c) {

        return this.map.keySet().removeAll(c);

    }

    @Override

    public boolean retainAll(Collection<?> c) {

        return this.map.keySet().retainAll(c);

    }

    @Override

    public Object[] toArray() {

        return this.map.keySet().toArray();

    }

    @Override

    public <T> T[] toArray(T[] a) {

        return this.map.keySet().toArray(a);

    }

    // use System.identityHashCode()

    @Override

    public int hashCode() {

        return this.map.keySet().hashCode();

    }

    // equals() uses containsAll which is correct

    /**

     * Returns a shallow copy of this <tt>HashSet</tt> instance: the elements themselves are not

     * cloned.

     *

     * @return a shallow copy of this set

     */

    public Object clone() {

        return new IdentityHashSet<E>(this);

    }

}