/*
 * Copyright (C) 2016 The Guava Authors
 *
 * Licensed 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.google.common.graph;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.collect.AbstractIterator;
import com.google.common.collect.UnmodifiableIterator;
import java.util.AbstractSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import org.checkerframework.checker.nullness.qual.Nullable;

A class to represent the set of edges connecting an (implicit) origin node to a target node.

The MultiEdgesConnecting<E>.outEdgeToNode map allows this class to work on networks with parallel edges. See EdgesConnecting for a class that is more efficient but forbids parallel edges.

Author:James Sexton
Type parameters:
  • <E> – Edge parameter type
/** * A class to represent the set of edges connecting an (implicit) origin node to a target node. * * <p>The {@link #outEdgeToNode} map allows this class to work on networks with parallel edges. See * {@link EdgesConnecting} for a class that is more efficient but forbids parallel edges. * * @author James Sexton * @param <E> Edge parameter type */
abstract class MultiEdgesConnecting<E> extends AbstractSet<E> { private final Map<E, ?> outEdgeToNode; private final Object targetNode; MultiEdgesConnecting(Map<E, ?> outEdgeToNode, Object targetNode) { this.outEdgeToNode = checkNotNull(outEdgeToNode); this.targetNode = checkNotNull(targetNode); } @Override public UnmodifiableIterator<E> iterator() { final Iterator<? extends Entry<E, ?>> entries = outEdgeToNode.entrySet().iterator(); return new AbstractIterator<E>() { @Override protected E computeNext() { while (entries.hasNext()) { Entry<E, ?> entry = entries.next(); if (targetNode.equals(entry.getValue())) { return entry.getKey(); } } return endOfData(); } }; } @Override public boolean contains(@Nullable Object edge) { return targetNode.equals(outEdgeToNode.get(edge)); } }