1 package org.eclipse.aether.util.graph.visitor;
2
3 /*
4 * Licensed to the Apache Software Foundation (ASF) under one
5 * or more contributor license agreements. See the NOTICE file
6 * distributed with this work for additional information
7 * regarding copyright ownership. The ASF licenses this file
8 * to you under the Apache License, Version 2.0 (the
9 * "License"); you may not use this file except in compliance
10 * with the License. You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing,
15 * software distributed under the License is distributed on an
16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17 * KIND, either express or implied. See the License for the
18 * specific language governing permissions and limitations
19 * under the License.
20 */
21
22 import org.eclipse.aether.graph.DependencyNode;
23
24 /**
25 * Generates a sequence of dependency nodes from a dependeny graph by traversing the graph in preorder. This visitor
26 * visits each node exactly once regardless how many paths within the dependency graph lead to the node such that the
27 * resulting node sequence is free of duplicates.
28 */
29 public final class PreorderNodeListGenerator
30 extends AbstractDepthFirstNodeListGenerator
31 {
32
33 /**
34 * Creates a new preorder list generator.
35 */
36 public PreorderNodeListGenerator()
37 {
38 }
39
40 @Override
41 public boolean visitEnter( DependencyNode node )
42 {
43 if ( !setVisited( node ) )
44 {
45 return false;
46 }
47
48 if ( node.getDependency() != null )
49 {
50 nodes.add( node );
51 }
52
53 return true;
54 }
55
56 @Override
57 public boolean visitLeave( DependencyNode node )
58 {
59 return true;
60 }
61
62 }