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Java example source code file (DirectedMultiNodeConnections.java)
This example Java source code file (DirectedMultiNodeConnections.java) is included in the alvinalexander.com
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The DirectedMultiNodeConnections.java Java example source code
/*
* 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.checkState;
import static com.google.common.graph.GraphConstants.EXPECTED_DEGREE;
import com.google.common.base.Predicate;
import com.google.common.collect.HashMultiset;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Maps;
import com.google.common.collect.Multiset;
import java.lang.ref.Reference;
import java.lang.ref.SoftReference;
import java.util.Collections;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import javax.annotation.Nullable;
/**
* An implementation of {@link NodeConnections} for directed networks with parallel edges.
*
* @author James Sexton
* @param <N> Node parameter type
* @param <E> Edge parameter type
*/
final class DirectedMultiNodeConnections<N, E> extends AbstractDirectedNodeConnections {
private DirectedMultiNodeConnections(Map<E, N> inEdges, Map outEdges) {
super(inEdges, outEdges);
}
static <N, E> DirectedMultiNodeConnections of() {
return new DirectedMultiNodeConnections<N, E>(
Maps.<E, N>newHashMapWithExpectedSize(EXPECTED_DEGREE),
Maps.<E, N>newHashMapWithExpectedSize(EXPECTED_DEGREE));
}
static <N, E> DirectedMultiNodeConnections ofImmutable(
Map<E, N> inEdges, Map outEdges) {
return new DirectedMultiNodeConnections<N, E>(
ImmutableMap.copyOf(inEdges), ImmutableMap.copyOf(outEdges));
}
private transient Reference<Multiset predecessorsReference;
@Override
public Set<N> predecessors() {
Multiset<N> predecessors = getReference(predecessorsReference);
if (predecessors == null) {
predecessors = HashMultiset.create(inEdgeMap.values());
predecessorsReference = new SoftReference<Multiset(predecessors);
}
return Collections.unmodifiableSet(predecessors.elementSet());
}
private transient Reference<Multiset successorsReference;
@Override
public Set<N> successors() {
Multiset<N> successors = getReference(successorsReference);
if (successors == null) {
successors = HashMultiset.create(outEdgeMap.values());
successorsReference = new SoftReference<Multiset(successors);
}
return Collections.unmodifiableSet(successors.elementSet());
}
@Override
public Set<E> edgesConnecting(final Object node) {
return Collections.unmodifiableSet(
Maps.filterEntries(outEdgeMap, new Predicate<Entry() {
@Override
public boolean apply(Entry<E, N> entry) {
return entry.getValue().equals(node);
}
}).keySet());
}
@Override
public N removeInEdge(Object edge) {
N node = super.removeInEdge(edge);
if (node != null) {
Multiset<N> predecessors = getReference(predecessorsReference);
if (predecessors != null) {
checkState(predecessors.remove(node));
}
}
return node;
}
@Override
public N removeOutEdge(Object edge) {
N node = super.removeOutEdge(edge);
if (node != null) {
Multiset<N> successors = getReference(successorsReference);
if (successors != null) {
checkState(successors.remove(node));
}
}
return node;
}
@Override
public boolean addInEdge(E edge, N node) {
if (super.addInEdge(edge, node)) {
Multiset<N> predecessors = getReference(predecessorsReference);
if (predecessors != null) {
checkState(predecessors.add(node));
}
return true;
}
return false;
}
@Override
public boolean addOutEdge(E edge, N node) {
if (super.addOutEdge(edge, node)) {
Multiset<N> successors = getReference(successorsReference);
if (successors != null) {
checkState(successors.add(node));
}
return true;
}
return false;
}
@Nullable private static <T> T getReference(@Nullable Reference reference) {
if (reference == null) {
return null;
}
return reference.get(); // can be null
}
}
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