| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| */ |
| package com.opensymphony.xwork2.config.providers; |
| |
| import java.util.Collections; |
| import java.util.HashMap; |
| import java.util.HashSet; |
| import java.util.Iterator; |
| import java.util.Map; |
| import java.util.NoSuchElementException; |
| import java.util.Set; |
| |
| public final class DirectedGraph<T> implements Iterable<T> { |
| private final Map<T, Set<T>> mGraph = new HashMap<T, Set<T>>(); |
| |
| /** |
| * Adds a new node to the graph. If the node already exists, this function is a no-op. |
| * |
| * @param node |
| * The node to add. |
| * @return Whether or not the node was added. |
| */ |
| public boolean addNode(T node) { |
| /* If the node already exists, don't do anything. */ |
| if (mGraph.containsKey(node)) |
| return false; |
| |
| /* Otherwise, add the node with an empty set of outgoing edges. */ |
| mGraph.put(node, new HashSet<T>()); |
| return true; |
| } |
| |
| /** |
| * Given a start node, and a destination, adds an arc from the start node to the destination. If an arc already exists, this operation is a no-op. |
| * If either endpoint does not exist in the graph, throws a NoSuchElementException. |
| * |
| * @param start |
| * The start node. |
| * @param dest |
| * The destination node. |
| * @throws NoSuchElementException |
| * If either the start or destination nodes do not exist. |
| */ |
| public void addEdge(T start, T dest) { |
| /* Confirm both endpoints exist. */ |
| if (!mGraph.containsKey(start)) { |
| throw new NoSuchElementException("The start node does not exist in the graph."); |
| } else if (!mGraph.containsKey(dest)) { |
| throw new NoSuchElementException("The destination node does not exist in the graph."); |
| } |
| |
| /* Add the edge. */ |
| mGraph.get(start).add(dest); |
| } |
| |
| /** |
| * Removes the edge from start to dest from the graph. If the edge does not exist, this operation is a no-op. If either endpoint does not exist, |
| * this throws a NoSuchElementException. |
| * |
| * @param start |
| * The start node. |
| * @param dest |
| * The destination node. |
| * @throws NoSuchElementException |
| * If either node is not in the graph. |
| */ |
| public void removeEdge(T start, T dest) { |
| /* Confirm both endpoints exist. */ |
| if (!mGraph.containsKey(start)) { |
| throw new NoSuchElementException("The start node does not exist in the graph."); |
| } else if (!mGraph.containsKey(dest)) { |
| throw new NoSuchElementException("The destination node does not exist in the graph."); |
| } |
| |
| mGraph.get(start).remove(dest); |
| } |
| |
| /** |
| * Given two nodes in the graph, returns whether there is an edge from the first node to the second node. If either node does not exist in the |
| * graph, throws a NoSuchElementException. |
| * |
| * @param start |
| * The start node. |
| * @param end |
| * The destination node. |
| * @return Whether there is an edge from start to end. |
| * @throws NoSuchElementException |
| * If either endpoint does not exist. |
| */ |
| public boolean edgeExists(T start, T end) { |
| /* Confirm both endpoints exist. */ |
| if (!mGraph.containsKey(start)) { |
| throw new NoSuchElementException("The start node does not exist in the graph."); |
| } else if (!mGraph.containsKey(end)) { |
| throw new NoSuchElementException("The end node does not exist in the graph."); |
| } |
| |
| return mGraph.get(start).contains(end); |
| } |
| |
| /** |
| * Given a node in the graph, returns an immutable view of the edges leaving that node as a set of endpoints. |
| * |
| * @param node |
| * The node whose edges should be queried. |
| * @return An immutable view of the edges leaving that node. |
| * @throws NoSuchElementException |
| * If the node does not exist. |
| */ |
| public Set<T> edgesFrom(T node) { |
| /* Check that the node exists. */ |
| Set<T> arcs = mGraph.get(node); |
| if (arcs == null) |
| throw new NoSuchElementException("Source node does not exist."); |
| |
| return Collections.unmodifiableSet(arcs); |
| } |
| |
| /** |
| * Returns an iterator that can traverse the nodes in the graph. |
| * |
| * @return An iterator that traverses the nodes in the graph. |
| */ |
| public Iterator<T> iterator() { |
| return mGraph.keySet().iterator(); |
| } |
| |
| /** |
| * Returns the number of nodes in the graph. |
| * |
| * @return The number of nodes in the graph. |
| */ |
| public int size() { |
| return mGraph.size(); |
| } |
| |
| /** |
| * Returns whether the graph is empty. |
| * |
| * @return Whether the graph is empty. |
| */ |
| public boolean isEmpty() { |
| return mGraph.isEmpty(); |
| } |
| } |