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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  package org.apache.hadoop.hbase.master.balancer;
19  
20  import java.util.Comparator;
21  
22  import org.apache.hadoop.hbase.HRegionInfo;
23  
24  /**
25   * The following comparator assumes that RegionId from HRegionInfo can represent
26   * the age of the region - larger RegionId means the region is younger. This
27   * comparator is used in balanceCluster() to account for the out-of-band regions
28   * which were assigned to the server after some other region server crashed.
29   */
30  class RegionInfoComparator implements Comparator<HRegionInfo> {
31    @Override
32    public int compare(HRegionInfo l, HRegionInfo r) {
33      long diff = r.getRegionId() - l.getRegionId();
34      if (diff < 0) return -1;
35      if (diff > 0) return 1;
36      return 0;
37    }
38  }