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 org.checkerframework.checker.nullness.qual.Nullable; 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 final class EdgesConnecting<E> extends AbstractSet<E> { 38 39 private final Map<?, E> nodeToOutEdge; 40 private final Object targetNode; 41 EdgesConnecting(Map<?, E> nodeToEdgeMap, Object targetNode)42 EdgesConnecting(Map<?, E> nodeToEdgeMap, Object targetNode) { 43 this.nodeToOutEdge = checkNotNull(nodeToEdgeMap); 44 this.targetNode = checkNotNull(targetNode); 45 } 46 47 @Override iterator()48 public UnmodifiableIterator<E> iterator() { 49 E connectingEdge = getConnectingEdge(); 50 return (connectingEdge == null) 51 ? ImmutableSet.<E>of().iterator() 52 : Iterators.singletonIterator(connectingEdge); 53 } 54 55 @Override size()56 public int size() { 57 return getConnectingEdge() == null ? 0 : 1; 58 } 59 60 @Override contains(@ullable Object edge)61 public boolean contains(@Nullable Object edge) { 62 E connectingEdge = getConnectingEdge(); 63 return (connectingEdge != null && connectingEdge.equals(edge)); 64 } 65 getConnectingEdge()66 private @Nullable E getConnectingEdge() { 67 return nodeToOutEdge.get(targetNode); 68 } 69 } 70