Generate the difference between two map Collection - Java java.util

Java examples for java.util:Map Operation

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Description

Generate the difference between two map Collection

Demo Code

/*// w  w w  . j  a  v  a  2s .  c  o  m
 * This file is part of the OpenSCADA project
 * Copyright (C) 2006-2010 TH4 SYSTEMS GmbH (http://th4-systems.com)
 *
 * OpenSCADA is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License version 3
 * only, as published by the Free Software Foundation.
 *
 * OpenSCADA is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License version 3 for more details
 * (a copy is included in the LICENSE file that accompanied this code).
 *
 * You should have received a copy of the GNU Lesser General Public License
 * version 3 along with OpenSCADA. If not, see
 * <http://opensource.org/licenses/lgpl-3.0.html> for a copy of the LGPLv3 License.
 */
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

public class Main{
    /**
     * Generate the difference between two maps
     * @param source the source map
     * @param target the target map
     * @return the difference
     */
    public static Map<String, Variant> diff(Map<String, Variant> source,
            final Map<String, Variant> target) {
        final Map<String, Variant> result;
        if (target != null) {
            result = new HashMap<String, Variant>(target);
        } else {
            result = Collections.emptyMap();
        }

        if (source == null) {
            source = Collections.emptyMap();
        }

        final Set<String> removeSet = new HashSet<String>();

        for (final Map.Entry<String, Variant> entry : source.entrySet()) {
            final Variant value = result.get(entry.getKey());
            if (value == null) {
                result.put(entry.getKey(), null);
            } else if (value.equals(entry.getValue())) {
                removeSet.add(entry.getKey());
            }
        }

        for (final String key : removeSet) {
            result.remove(key);
        }

        return result;
    }
}

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