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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 lowest one.
29   *
30   * @since 2.0.0
31   */
32  public final class LowestVersionFilter implements VersionFilter {
33      private final int count;
34  
35      /**
36       * Creates a new instance of this version filter.
37       */
38      public LowestVersionFilter() {
39          this.count = 1;
40      }
41  
42      /**
43       * Creates a new instance of this version filter.
44       */
45      public LowestVersionFilter(int count) {
46          if (count < 1) {
47              throw new IllegalArgumentException("Count should be greater or equal to 1");
48          }
49          this.count = count;
50      }
51  
52      @Override
53      public void filterVersions(VersionFilterContext context) {
54          if (context.getCount() <= count) {
55              return;
56          }
57          // iterator comes in ascending order, basically we "step over" (leave) first few
58          int stepOver = count;
59          Iterator<Version> it = context.iterator();
60          while (it.hasNext()) {
61              it.next();
62              stepOver--;
63              if (stepOver < 0) {
64                  it.remove();
65              }
66          }
67      }
68  
69      @Override
70      public VersionFilter deriveChildFilter(DependencyCollectionContext context) {
71          return this;
72      }
73  
74      @Override
75      public boolean equals(Object obj) {
76          if (this == obj) {
77              return true;
78          } else if (null == obj || !getClass().equals(obj.getClass())) {
79              return false;
80          }
81          return true;
82      }
83  
84      @Override
85      public int hashCode() {
86          return getClass().hashCode();
87      }
88  }