de.flapdoodle.logparser.collections.Collections.java Source code

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Here is the source code for de.flapdoodle.logparser.collections.Collections.java

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/**
 * Copyright (C) 2013
 *   Michael Mosmann <michael@mosmann.de>
 *
 * with contributions from
 *    ${lic.developers}
 *
 * 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 de.flapdoodle.logparser.collections;

import java.util.Collection;
import java.util.Map;

import com.google.common.collect.Maps;
import com.google.common.collect.Sets;

public class Collections {

    private Collections() {
        // no instance
    }

    public static <K, V> Map<K, V> join(Collection<? extends Map<K, V>> maps) {
        Map<K, V> ret = Maps.newHashMap();
        for (Map<K, V> map : maps) {
            ret = join(ret, map);
        }
        return ret;
    }

    public static <K, V> Map<K, V> join(Map<K, V>... maps) {
        Map<K, V> ret = Maps.newHashMap();
        for (Map<K, V> map : maps) {
            ret = join(ret, map);
        }
        return ret;
    }

    public static <K, V> Map<K, V> join(Map<K, V> a, Map<K, V> b) {
        Map<K, V> ret = Maps.newHashMap(a);
        ret.putAll(b);
        if (ret.size() != a.size() + b.size()) {
            throw new IllegalArgumentException(
                    "Map contains same keys: " + Sets.intersection(a.keySet(), b.keySet()));
        }
        return ret;
    }

}