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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.visitor;
20  
21  import org.eclipse.aether.graph.DependencyNode;
22  
23  /**
24   * Generates a sequence of dependency nodes from a dependency graph by traversing the graph in postorder. This visitor
25   * visits each node exactly once regardless how many paths within the dependency graph lead to the node such that the
26   * resulting node sequence is free of duplicates.
27   * <p>
28   * The newer classes {@link AbstractDependencyNodeConsumerVisitor} and {@link NodeListGenerator} offer
29   * similar capabilities but are pluggable. Use of this class, while not deprecated, is discouraged. This class
30   * is not used in Resolver and is kept only for backward compatibility reasons.
31   *
32   * @see PostorderDependencyNodeConsumerVisitor
33   * @see NodeListGenerator
34   *
35   * @deprecated See {@link PostorderDependencyNodeConsumerVisitor} that is more versatile.
36   */
37  @Deprecated
38  public final class PostorderNodeListGenerator extends AbstractDepthFirstNodeListGenerator {
39  
40      private final Stack<Boolean> visits;
41  
42      /**
43       * Creates a new postorder list generator.
44       */
45      public PostorderNodeListGenerator() {
46          visits = new Stack<>();
47      }
48  
49      @Override
50      public boolean visitEnter(DependencyNode node) {
51          boolean visited = !setVisited(node);
52  
53          visits.push(visited);
54  
55          return !visited;
56      }
57  
58      @Override
59      public boolean visitLeave(DependencyNode node) {
60          Boolean visited = visits.pop();
61  
62          if (visited) {
63              return true;
64          }
65  
66          if (node.getDependency() != null) {
67              nodes.add(node);
68          }
69  
70          return true;
71      }
72  }