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Provides common utility functions

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/*
 * Copyright (c) CQSE GmbH
 *
 * 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.
 */

package org.conqat.lib.commons.collections;

import java.util.Collection;
import java.util.IdentityHashMap;

/**
 * This class implements a set based on referential equality similar to JDK class
 * {@link IdentityHashMap}. This class can be e.g. used to implement listener lists that should not
 * rely on the listeners equals()-methods.
 * 
 * The implementation is based on class {@link java.util.HashSet} that also uses an underlying hash
 * map.
 */
public class IdentityHashSet extends MapBackedSetBase {

	public IdentityHashSet() {
		super(new IdentityHashMap<>());
	}

	/** Create new identity hash set from an existing collection. */
	public IdentityHashSet(Collection collection) {
		this(collection.size());
		addAll(collection);
	}

	/** Create new identity hash set with an expected maximum size. */
	public IdentityHashSet(int expectedMaxSize) {
		super(new IdentityHashMap<>(expectedMaxSize));
	}

	/**
	 * Returns a shallow copy of this IdentityHashSet instance: the elements themselves are not
	 * cloned.
	 * 
	 * @return a shallow copy of this set.
	 */
	@Override
	public IdentityHashSet clone() {
		return new IdentityHashSet<>(this);
	}
}