Gets a Map containing all of the entries from the maps provided. - Java Collection Framework

Java examples for Collection Framework:Map

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Description

Gets a Map containing all of the entries from the maps provided.

Demo Code

/*//from   ww  w .j  av  a 2s. c  o m
 * Copyright Terracotta, 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.java2s;
import java.util.ArrayList;

import java.util.HashMap;
import java.util.HashSet;

import java.util.List;
import java.util.Map;
import java.util.Set;

public class Main {
    /**
     * Gets a {@code Map} containing all of the entries from the maps provided.
     *
     * @param map1 the first {@code Map} instance to combine
     * @param map2 the second {@code Map} instance to combine
     *
     * @return a new {@code Map} containing all of the entries
     */
    static Map<String, String> union(final Map<String, String> map1,
            final Map<String, String> map2) {
        final List<Map<String, String>> maps = new ArrayList<Map<String, String>>();
        maps.add(map1);
        maps.add(map2);
        return unionMaps(maps);
    }

    /**
     * Gets a {@code Map} containing all of the entries from the maps provided.
     *
     * @param map1 the first {@code Map} instance to combine
     * @param map2 the second {@code Map} instance to combine
     * @param map3 the third {@code Map} instance to combine
     *
     * @return a new {@code Map} containing all of the entries
     */
    static Map<String, String> union(final Map<String, String> map1,
            final Map<String, String> map2, final Map<String, String> map3) {
        final List<Map<String, String>> maps = new ArrayList<Map<String, String>>();
        maps.add(map1);
        maps.add(map2);
        maps.add(map3);
        return unionMaps(maps);
    }

    /**
     * Gets a {@code Set} containing all of the elements from the sets provided
     *
     * @param set1 the first {@code Set} instance to combine
     * @param set2 the second {@code Set} instance to combine
     *
     * @return a new {@code Set} containing all of the elements
     */
    static Set<String> union(final Set<String> set1, final Set<String> set2) {
        final List<Set<String>> sets = new ArrayList<Set<String>>();
        sets.add(set1);
        sets.add(set2);
        return unionSets(sets);
    }

    /**
     * Gets a {@code Map} containing all of the entries from the maps provided.
     *
     * @param maps the {@code Map} instances to combine
     *
     * @return a new {@code Map} containing all of the entries
     */
    private static Map<String, String> unionMaps(
            final List<Map<String, String>> maps) {
        final Map<String, String> union = new HashMap<String, String>();
        for (Map<String, String> map : maps) {
            union.putAll(map);
        }
        return union;
    }

    /**
     * Gets a {@code Set} containing all of the entries from the sets provided.
     *
     * @param sets the {@code Set} instances to combine
     *
     * @return a new {@code Set} containing all of the elements
     */
    private static Set<String> unionSets(final List<Set<String>> sets) {
        final Set<String> union = new HashSet<String>();
        for (final Set<String> set : sets) {
            union.addAll(set);
        }
        return union;
    }
}

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