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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.io.Serializable;
import java.util.Collections;
import java.util.Map;

/**
 * This is a wrapper for a {@link Map} prohibiting all calls which would modify its contents. As the
 * construction of this class is performed in constant time it is preferred over copying the map
 * (which takes linear time). Using this class is also preferred to using the
 * unmodifiableX() in class {@link Collections} as they return the collection base type
 * that does not signal, that the object ist unmodifiable. Using the classes in this package makes
 * unmodifiability more explicit.
 * 
 * All prohibited methods throw an {@link UnsupportedOperationException}. The class is nearly the
 * same as the one returned by {@link Collections#unmodifiableMap(Map)}, but by making it a public
 * class we can make the return value of some methods more explicit.
 * 
 * This map is serializable if the wrapped map is serializable.
 */
public class UnmodifiableMap implements Map, Serializable {

	/** Version used for serialization. */
	private static final long serialVersionUID = 1;

	/** The underlying map. */
	private final Map map;

	/**
	 * Creates a new unmodifiable map from another map. All modifications to the underlying map will
	 * directly be visible in this wrapper.
	 */
	public UnmodifiableMap(Map m) {
		if (m == null) {
			throw new IllegalArgumentException("Underlying map may not be null!");
		}
		this.map = m;
	}

	/** {@inheritDoc} */
	@Override
	public boolean isEmpty() {
		return map.isEmpty();
	}

	/** {@inheritDoc} */
	@Override
	public int size() {
		return map.size();
	}

	/** {@inheritDoc} */
	@Override
	public boolean containsKey(Object key) {
		return map.containsKey(key);
	}

	/** {@inheritDoc} */
	@Override
	public boolean containsValue(Object value) {
		return map.containsValue(value);
	}

	/** {@inheritDoc} */
	@Override
	public V get(Object key) {
		return map.get(key);
	}

	/** {@inheritDoc} */
	@Override
	public UnmodifiableSet keySet() {
		return new UnmodifiableSet<>(map.keySet());
	}

	/** {@inheritDoc} */
	@Override
	public UnmodifiableCollection values() {
		return new UnmodifiableCollection<>(map.values());
	}

	/** {@inheritDoc} */
	@Override
	public UnmodifiableSet> entrySet() {
		return new UnmodifiableSet<>(map.entrySet());
	}

	/** Operation is not supported. */
	@Override
	public void clear() {
		throw new UnsupportedOperationException();
	}

	/** Operation is not supported. */
	@Override
	public V put(K arg0, V arg1) {
		throw new UnsupportedOperationException();
	}

	/** Operation is not supported. */
	@Override
	public void putAll(Map arg0) {
		throw new UnsupportedOperationException();
	}

	/** Operation is not supported. */
	@Override
	public V remove(Object arg0) {
		throw new UnsupportedOperationException();
	}

	/**
	 * Returns a string representation of this map.
	 */
	@Override
	public String toString() {
		return map.toString();
	}

	/** {@inheritDoc} */
	@Override
	public boolean equals(Object obj) {
		if (this == obj) {
			return true;
		}
		if (obj instanceof UnmodifiableMap) {
			return map.equals(((UnmodifiableMap) obj).map);
		}
		return map.equals(obj);
	}

	/** {@inheritDoc} */
	@Override
	public int hashCode() {
		return map.hashCode();
	}
}