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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.commons.configuration2.tree;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

/**
 * 
 * A simple data class used by node models to store parameters of an update operation.
 * 
 * 
 * The {@code Configuration} interface provides a method for setting the value of a given key. The passed in value can
 * be a single object or a collection of values. This makes an update operation rather complicated because a collection
 * of query results selected by the passed in key has to be matched to another collection of values - and both
 * collections can have different sizes. Therefore, an update operation may involve changing of existing nodes, adding
 * new nodes (if there are more values than currently existing nodes), and removing nodes (if there are more existing
 * nodes than provided values). This class collects all this information making it possible to actually perform the
 * update based on a passed in instance.
 * 
 *
 * @since 2.0
 * @param  the type of nodes involved in this update operation
 */
public class NodeUpdateData {
    /**
     * Creates an unmodifiable defensive copy of the passed in collection with may be null.
     *
     * @param col the collection to be copied
     * @param  the element type of the collection
     * @return the unmodifiable copy
     */
    private static  Collection copyCollection(final Collection col) {
        if (col == null) {
            return Collections.emptySet();
        }
        return Collections.unmodifiableCollection(new ArrayList<>(col));
    }

    /**
     * Creates an unmodifiable defensive copy of the passed in map which may be null.
     *
     * @param map the map to be copied
     * @param  the type of the keys involved
     * @param  the type of the values involved
     * @return the unmodifiable copy
     */
    private static  Map copyMap(final Map map) {
        if (map == null) {
            return Collections.emptyMap();
        }
        return Collections.unmodifiableMap(new HashMap<>(map));
    }

    /** The map with the query results whose value has to be changed. */
    private final Map, Object> changedValues;

    /** The collection with the new values to be added. */
    private final Collection