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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,
13   * software distributed under the License is distributed on an
14   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15   * KIND, either express or implied.  See the License for the
16   * specific language governing permissions and limitations
17   * under the License.
18   */
19  package org.eclipse.aether.util.graph.version;
20  
21  import java.util.Iterator;
22  
23  import org.eclipse.aether.collection.DependencyCollectionContext;
24  import org.eclipse.aether.collection.VersionFilter;
25  import org.eclipse.aether.version.Version;
26  
27  /**
28   * A version filter that excludes any version except the highest one.
29   */
30  public final class HighestVersionFilter implements VersionFilter {
31      private final int count;
32  
33      /**
34       * Creates a new instance of this version filter.
35       */
36      public HighestVersionFilter() {
37          this.count = 1;
38      }
39  
40      /**
41       * Creates a new instance of this version filter.
42       */
43      public HighestVersionFilter(int count) {
44          if (count < 1) {
45              throw new IllegalArgumentException("Count should be greater or equal to 1");
46          }
47          this.count = count;
48      }
49  
50      @Override
51      public void filterVersions(VersionFilterContext context) {
52          if (context.getCount() <= count) {
53              return;
54          }
55          // iterator comes in ascending order, basically we "step over" (remove) first few
56          int stepOver = context.getCount() - count;
57          Iterator<Version> it = context.iterator();
58          while (it.hasNext()) {
59              it.next();
60              stepOver--;
61              if (stepOver >= 0) {
62                  it.remove();
63              }
64          }
65      }
66  
67      @Override
68      public VersionFilter deriveChildFilter(DependencyCollectionContext context) {
69          return this;
70      }
71  
72      @Override
73      public boolean equals(Object obj) {
74          if (this == obj) {
75              return true;
76          } else if (null == obj || !getClass().equals(obj.getClass())) {
77              return false;
78          }
79          return true;
80      }
81  
82      @Override
83      public int hashCode() {
84          return getClass().hashCode();
85      }
86  }