获取一个新的集合，该集合是所提供集合的交错并集。

/*

 * 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.

 */

import java.util.ArrayList;

import java.util.Collection;

import java.util.Collections;
/*
 from N o w J a v a . c o m - 时代Java 
*/

import java.util.HashMap;

import java.util.HashSet;

import java.util.LinkedHashMap;

import java.util.LinkedHashSet;

import java.util.List;

import java.util.Map;

import java.util.Set;


public class Main{

    public static void main(String[] argv) throws Exception{

        List keySets = java.util.Arrays.asList("asdf","nowjava.com");

        System.out.println(fanIn(keySets));
        /* from 
        时代Java公众号 - nowjava.com*/

    }

    /**

     * Entries for populating {@link org.ehcache.spi.cache.Store Store} and

     * {@link org.ehcache.spi.loader.CacheLoader CacheLoader} instances in the

     * unit tests.  The entries used are generally subset using the key sets

     * {@link #KEY_SET_A}, {@link #KEY_SET_B}, {@link #KEY_SET_C}, and/or

     * {@link #KEY_SET_F}.

     * <p/>

     * Some tests are dependent on the order of the keys/entries.  In general,

     * for each key set ('xxxXn'), the keys/entries must be ordered by 'n'.

     */

    static final Map<String, String> TEST_ENTRIES;

    /**

     * Gets a new {@code Set} that is the interleaved union of the {@code Set}s provided.

     *

     * @param keySet1 the first {@code Set} of keys to appear in the result {@code Set}

     * @param keySet2 the second {@code Set} of keys to appear in the result {@code Set}

     *

     * @return a new, modifiable {@code Set} holding the designated keys

     *

     * @see #fanIn(java.util.List)

     */

    static Set<String> fanIn(final Set<String> keySet1,

            final Set<String> keySet2) {

        final List<Set<String>> keySets = new ArrayList<Set<String>>();

        keySets.add(keySet1);

        keySets.add(keySet2);

        return fanIn(keySets);

    }

    /**

     * Gets a new {@code Set} that is the interleaved union of the {@code Set}s provided.

     *

     * @param keySet1 the first {@code Set} of keys to appear in the result {@code Set}

     * @param keySet2 the second {@code Set} of keys to appear in the result {@code Set}

     * @param keySet3 the third {@code Set} of keys to appear in the result {@code Set}

     *

     * @return a new, modifiable {@code Set} holding the designated keys

     *

     * @see #fanIn(java.util.List)

     */

    static Set<String> fanIn(final Set<String> keySet1,

            final Set<String> keySet2, final Set<String> keySet3) {

        final List<Set<String>> keySets = new ArrayList<Set<String>>();

        keySets.add(keySet1);

        keySets.add(keySet2);

        keySets.add(keySet3);

        return fanIn(keySets);

    }

    /**

     * Gets a new {@code Set} that is the interleaved union of the {@code Set}s provided.

     *

     * @param keySet1 the first {@code Set} of keys to appear in the result {@code Set}

     * @param keySet2 the second {@code Set} of keys to appear in the result {@code Set}

     * @param keySet3 the third {@code Set} of keys to appear in the result {@code Set}

     * @param keySet4 the fourth {@code Set} of keys to appear in the result {@code Set}

     *

     * @return a new, modifiable {@code Set} holding the designated keys

     *

     * @see #fanIn(java.util.List)

     */

    static Set<String> fanIn(final Set<String> keySet1,

            final Set<String> keySet2, final Set<String> keySet3,

            final Set<String> keySet4) {

        final List<Set<String>> keySets = new ArrayList<Set<String>>();

        keySets.add(keySet1);

        keySets.add(keySet2);

        keySets.add(keySet3);

        keySets.add(keySet4);

        return fanIn(keySets);

    }