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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.hadoop.hbase.util;
20  
21  import java.util.ArrayList;
22  import java.util.Collections;
23  import java.util.List;
24  
25  import org.apache.hadoop.classification.InterfaceAudience;
26  
27  /**
28   * Utility methods for Iterable including null-safe handlers.
29   */
30  @InterfaceAudience.Private
31  public class IterableUtils {
32  
33    private static final List<Object> EMPTY_LIST = Collections
34        .unmodifiableList(new ArrayList<Object>(0));
35  
36    @SuppressWarnings("unchecked")
37    public static <T> Iterable<T> nullSafe(Iterable<T> in) {
38      if (in == null) {
39        return (List<T>) EMPTY_LIST;
40      }
41      return in;
42    }
43  
44  }