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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *     http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  package org.apache.giraph.utils;
20  
21  import com.google.common.collect.Iterators;
22  
23  import java.util.Iterator;
24  
25  /**
26   * Singleton class for empty iterables.
27   *
28   * @param <T> Element type
29   */
30  public class EmptyIterable<T> implements Iterable<T> {
31    /** Singleton empty iterable */
32    private static final EmptyIterable EMPTY_ITERABLE = new EmptyIterable();
33  
34    /**
35     * Get the singleton empty iterable
36     *
37     * @param <T> Element type
38     * @return Singleton empty iterable
39     */
40    public static <T> Iterable<T> get() {
41      return (Iterable<T>) EMPTY_ITERABLE;
42    }
43  
44    @Override
45    public Iterator<T> iterator() {
46      return Iterators.emptyIterator();
47    }
48  }
49