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Utility classes developed at Adrian Smith Software (A.S.S.)

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package com.databasesandlife.util.gwtsafe;

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

/**
 * Like a {@link java.util.HashSet} but compares objects based on the Java object identity.
 *
 * Does not implement {@link java.util.Set} interface because it is less generic than it could be;
 * and in the project where this was required implementing the interface was not required.
 *
 * @author This source is copyright Adrian Smith and licensed under the LGPL 3.
 * @see Project on GitHub
 */
public class IdentityHashSet implements Iterable, Serializable {

    protected final IdentityHashMap map = new IdentityHashMap<>();

    // Constructors
    public IdentityHashSet() { }
    public IdentityHashSet(Collection collection) { for (var x : collection) add(x); }

    // Mutators
    public void add(T obj) { map.put(obj, null); }
    public void addAll(Collection objects) { for (var o : objects) add(o); }
    public void addAll(T[] objects) { for (var o : objects) add(o); }
    public void remove(T obj) { map.remove(obj); }

    // Query
    public boolean contains(T obj) { return map.containsKey(obj); }
    public Iterator iterator() { return map.keySet().iterator(); }
    public int size() { return map.size(); }
    public boolean isEmpty() { return map.isEmpty(); }
}