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Norconex Commons Lang is a Java library containing utility classes that complements the Java API and are not found in commonly available libraries (such as the great Apache Commons Lang, which it relies on).
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/* Copyright 2010-2016 Norconex Inc.
 *
 * 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 com.norconex.commons.lang.map;

import java.io.Serializable;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

/**
 * A map implementation that reports changes to added {@link IMapChangeListener}
 * instance.  Changes are triggered when a value change is detected
 * in the following method calls: {@link #put(Object, Object)}, 
 * {@link #putAll(Map)}, {@link #remove(Object)}, and {@link #clear()}.
 * This class will not detect changes made to key or value objects modified
 * outside this class.
 * This class can be used as a decorator to other {@link Map} implementations.
 * 
 * @author Pascal Essiembre
 * @since 1.4
 *
 * @param  the type of keys maintained by the map we are observing
 * @param  the type of mapped values
 */
public class ObservableMap implements Map, Serializable {

    private static final long serialVersionUID = 8109864235479497466L;

    private final MapChangeSupport mcs = new MapChangeSupport<>(this);    
    private final Map map;
    
    public ObservableMap() {
        this(null);
    }
    /**
     * Decorates map argument as an {@code ObservableMap}.
     * @param map the Map to decorate 
     */
    public ObservableMap(Map map) {
        if (map == null) {
            this.map = new HashMap<>();
        } else {
            this.map = map;
        }
    }

    /**
     * Adds a map change listener.
     * @param listener change listener
     */
    public void addMapChangeListener(IMapChangeListener listener) {
        this.mcs.addMapChangeListener(listener);
    }
    /**
     * Removes a map change listener.
     * @param listener change listener
     */
    public void removeMapChangeListener(IMapChangeListener listener) {
        this.mcs.removeMapChangeListener(listener);
    }
    
    @Override
    public int size() {
        return map.size();
    }
    @Override
    public boolean isEmpty() {
        return map.isEmpty();
    }
    @Override
    public boolean containsKey(Object key) {
        return map.containsKey(key);
    }
    @Override
    public boolean containsValue(Object value) {
        return map.containsValue(value);
    }
    @Override
    public V get(Object key) {
        return map.get(key);
    }
    @Override
    public V put(K key, V value) {
        if (mcs.isEmpty()) {
            return map.put(key, value);
        }
        V oldValue = map.put(key, value);
        mcs.fireMapChange(key, oldValue, value);
        return oldValue;
    }
    @SuppressWarnings("unchecked")
    @Override
    public V remove(Object key) {
        if (mcs.isEmpty()) {
            return map.remove(key);
        }
        V oldValue = map.remove(key);
        mcs.fireMapChange((K) key, oldValue, null);
        return oldValue;
    }
    @Override
    public void putAll(Map m) {
        if (mcs.isEmpty()) {
            map.putAll(m);
            return;
        }
        Iterator> it = 
                m.entrySet().iterator();
        while (it.hasNext()) {
            Map.Entry entry = it.next();
            put(entry.getKey(), entry.getValue());
        } 
    }
    @Override
    public void clear() {
        if (mcs.isEmpty()) {
            map.clear();
            return;
        }
        Map oldMap = new HashMap<>(map);
        map.clear();
        Iterator> it = oldMap.entrySet().iterator();
        while (it.hasNext()) {
            Map.Entry entry = it.next();
            mcs.fireMapChange(entry.getKey(), entry.getValue(), null);
        }
    }
    @Override
    public Set keySet() {
        return map.keySet();
    }
    @Override
    public Collection values() {
        return map.values();
    }
    @Override
    public Set> entrySet() {
        return map.entrySet();
    }

    @Override
    public String toString() {
        return "ObservableMap [map=" + map + "]";
    }

}