1 /*
2 * Copyright (C) 2016 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 package com.google.common.graph;
18
19 import static com.google.common.base.Preconditions.checkNotNull;
20
21 import com.google.common.collect.AbstractIterator;
22 import com.google.common.collect.UnmodifiableIterator;
23 import java.util.AbstractSet;
24 import java.util.Iterator;
25 import java.util.Map;
26 import java.util.Map.Entry;
27 import javax.annotation.CheckForNull;
28
29 /**
30 * A class to represent the set of edges connecting an (implicit) origin node to a target node.
31 *
32 * <p>The {@link #outEdgeToNode} map allows this class to work on networks with parallel edges. See
33 * {@link EdgesConnecting} for a class that is more efficient but forbids parallel edges.
34 *
35 * @author James Sexton
36 * @param <E> Edge parameter type
37 */
38 @ElementTypesAreNonnullByDefault
39 abstract class MultiEdgesConnecting<E> extends AbstractSet<E> {
40
41 private final Map<E, ?> outEdgeToNode;
42 private final Object targetNode;
43
44 MultiEdgesConnecting(Map<E, ?> outEdgeToNode, Object targetNode) {
45 this.outEdgeToNode = checkNotNull(outEdgeToNode);
46 this.targetNode = checkNotNull(targetNode);
47 }
48
49 @Override
50 public UnmodifiableIterator<E> iterator() {
51 final Iterator<? extends Entry<E, ?>> entries = outEdgeToNode.entrySet().iterator();
52 return new AbstractIterator<E>() {
53 @Override
54 protected E computeNext() {
55 while (entries.hasNext()) {
56 Entry<E, ?> entry = entries.next();
57 if (targetNode.equals(entry.getValue())) {
58 return entry.getKey();
59 }
60 }
61 return endOfData();
62 }
63 };
64 }
65
66 @Override
67 public boolean contains(@CheckForNull Object edge) {
68 return targetNode.equals(outEdgeToNode.get(edge));
69 }
70 }