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.ImmutableSet;
22 import com.google.common.collect.Iterators;
23 import com.google.common.collect.UnmodifiableIterator;
24 import java.util.AbstractSet;
25 import java.util.Map;
26 import javax.annotation.CheckForNull;
27
28 /**
29 * A class to represent the set of edges connecting an (implicit) origin node to a target node.
30 *
31 * <p>The {@link #nodeToOutEdge} map means this class only works on networks without parallel edges.
32 * See {@link MultiEdgesConnecting} for a class that works with parallel edges.
33 *
34 * @author James Sexton
35 * @param <E> Edge parameter type
36 */
37 @ElementTypesAreNonnullByDefault
38 final class EdgesConnecting<E> extends AbstractSet<E> {
39
40 private final Map<?, E> nodeToOutEdge;
41 private final Object targetNode;
42
43 EdgesConnecting(Map<?, E> nodeToEdgeMap, Object targetNode) {
44 this.nodeToOutEdge = checkNotNull(nodeToEdgeMap);
45 this.targetNode = checkNotNull(targetNode);
46 }
47
48 @Override
49 public UnmodifiableIterator<E> iterator() {
50 E connectingEdge = getConnectingEdge();
51 return (connectingEdge == null)
52 ? ImmutableSet.<E>of().iterator()
53 : Iterators.singletonIterator(connectingEdge);
54 }
55
56 @Override
57 public int size() {
58 return getConnectingEdge() == null ? 0 : 1;
59 }
60
61 @Override
62 public boolean contains(@CheckForNull Object edge) {
63 E connectingEdge = getConnectingEdge();
64 return (connectingEdge != null && connectingEdge.equals(edge));
65 }
66
67 @CheckForNull
68 private E getConnectingEdge() {
69 return nodeToOutEdge.get(targetNode);
70 }
71 }