1 package org.apache.commons.graph;
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 /**
23 * An {@code Edge} is the link that connect a pair of {@link Vertex}.
24 *
25 * A {@link Graph} in which {@link Edge}s have no orientation, {@link Vertex} members are not ordered pairs.
26 *
27 * In a {@link DirectedGraph}, {@link Edge}s have orientation, so relation expressed by the {@link Edge} has to be
28 * intended from {@link #getHead()} to {@link #getTail()}.
29 *
30 * @param <V> the Graph vertices type
31 */
32 public interface Edge<V extends Vertex>
33 {
34
35 /**
36 * Return the head of this edge.
37 *
38 * @return the head of this edge.
39 */
40 V getHead();
41
42 /**
43 * Return the tail of this edge.
44 *
45 * @return the tail of this edge.
46 */
47 V getTail();
48
49 }