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 postorder. 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 PostorderNodeListGenerator 30 extends AbstractDepthFirstNodeListGenerator 31 { 32 33 private final Stack<Boolean> visits; 34 35 /** 36 * Creates a new postorder list generator. 37 */ 38 public PostorderNodeListGenerator() 39 { 40 visits = new Stack<Boolean>(); 41 } 42 43 @Override 44 public boolean visitEnter( DependencyNode node ) 45 { 46 boolean visited = !setVisited( node ); 47 48 visits.push( visited ); 49 50 if ( visited ) 51 { 52 return false; 53 } 54 55 return true; 56 } 57 58 @Override 59 public boolean visitLeave( DependencyNode node ) 60 { 61 Boolean visited = visits.pop(); 62 63 if ( visited ) 64 { 65 return true; 66 } 67 68 if ( node.getDependency() != null ) 69 { 70 nodes.add( node ); 71 } 72 73 return true; 74 } 75 76 }