001/* 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, 013 * software distributed under the License is distributed on an 014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 015 * KIND, either express or implied. See the License for the 016 * specific language governing permissions and limitations 017 * under the License. 018 */ 019package org.eclipse.aether.util.graph.visitor; 020 021import java.util.function.Consumer; 022 023import org.eclipse.aether.graph.DependencyNode; 024 025/** 026 * Processes dependency graph by traversing the graph in postorder. This visitor visits each node exactly once 027 * regardless how many paths within the dependency graph lead to the node such that the resulting node sequence is 028 * free of duplicates. 029 * 030 * @since TBD 031 */ 032public final class PostorderDependencyNodeConsumerVisitor extends AbstractDependencyNodeConsumerVisitor { 033 034 public static final String NAME = "postOrder"; 035 036 private final Stack<Boolean> visits; 037 038 /** 039 * Creates a new postorder list generator. 040 */ 041 public PostorderDependencyNodeConsumerVisitor(Consumer<DependencyNode> nodeConsumer) { 042 super(nodeConsumer); 043 visits = new Stack<>(); 044 } 045 046 @Override 047 public boolean visitEnter(DependencyNode node) { 048 boolean visited = !setVisited(node); 049 visits.push(visited); 050 return !visited; 051 } 052 053 @Override 054 public boolean visitLeave(DependencyNode node) { 055 Boolean visited = visits.pop(); 056 if (visited) { 057 return true; 058 } 059 nodeConsumer.accept(node); 060 return true; 061 } 062}