| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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 org.apache.tinkerpop.gremlin.process.traversal.util; |
| |
| import org.apache.tinkerpop.gremlin.process.traversal.Bytecode; |
| import org.apache.tinkerpop.gremlin.process.traversal.Step; |
| import org.apache.tinkerpop.gremlin.process.traversal.Traversal; |
| import org.apache.tinkerpop.gremlin.process.traversal.TraversalSideEffects; |
| import org.apache.tinkerpop.gremlin.process.traversal.TraversalStrategies; |
| import org.apache.tinkerpop.gremlin.process.traversal.Traverser; |
| import org.apache.tinkerpop.gremlin.process.traversal.TraverserGenerator; |
| import org.apache.tinkerpop.gremlin.process.traversal.step.TraversalParent; |
| import org.apache.tinkerpop.gremlin.process.traversal.step.util.EmptyStep; |
| import org.apache.tinkerpop.gremlin.process.traversal.traverser.TraverserRequirement; |
| import org.apache.tinkerpop.gremlin.structure.Graph; |
| |
| import java.util.Collections; |
| import java.util.Iterator; |
| import java.util.List; |
| import java.util.Optional; |
| import java.util.Set; |
| |
| /** |
| * @author Marko A. Rodriguez (http://markorodriguez.com) |
| */ |
| public final class EmptyTraversal<S, E> implements Traversal.Admin<S, E> { |
| |
| private static final EmptyTraversal INSTANCE = new EmptyTraversal(); |
| private static final TraversalSideEffects SIDE_EFFECTS = EmptyTraversalSideEffects.instance(); |
| private static final TraversalStrategies STRATEGIES = EmptyTraversalStrategies.instance(); |
| |
| public static <A, B> EmptyTraversal<A, B> instance() { |
| return INSTANCE; |
| } |
| |
| protected EmptyTraversal() { |
| |
| } |
| |
| public Bytecode getBytecode() { |
| return new Bytecode(); |
| } |
| |
| @Override |
| public Traversal.Admin<S, E> asAdmin() { |
| return this; |
| } |
| |
| @Override |
| public boolean hasNext() { |
| return false; |
| } |
| |
| @Override |
| public E next() { |
| throw FastNoSuchElementException.instance(); |
| } |
| |
| @Override |
| public TraversalSideEffects getSideEffects() { |
| return SIDE_EFFECTS; |
| } |
| |
| @Override |
| public void applyStrategies() { |
| |
| } |
| |
| @Override |
| public void addStarts(final Iterator<Traverser.Admin<S>> starts) { |
| |
| } |
| |
| @Override |
| public void addStart(final Traverser.Admin<S> start) { |
| |
| } |
| |
| @Override |
| public <E2> Traversal.Admin<S, E2> addStep(final Step<?, E2> step) { |
| return instance(); |
| } |
| |
| @Override |
| public List<Step> getSteps() { |
| return Collections.emptyList(); |
| } |
| |
| @Override |
| public EmptyTraversal<S, E> clone() { |
| return instance(); |
| } |
| |
| @Override |
| public boolean isLocked() { |
| return true; |
| } |
| |
| @Override |
| public TraverserGenerator getTraverserGenerator() { |
| return null; |
| } |
| |
| @Override |
| public void setSideEffects(final TraversalSideEffects sideEffects) { |
| } |
| |
| @Override |
| public TraversalStrategies getStrategies() { |
| return STRATEGIES; |
| } |
| |
| @Override |
| public void setParent(final TraversalParent step) { |
| |
| } |
| |
| @Override |
| public TraversalParent getParent() { |
| return EmptyStep.instance(); |
| } |
| |
| @Override |
| public void setStrategies(final TraversalStrategies traversalStrategies) { |
| |
| } |
| |
| @Override |
| public <S2, E2> Traversal.Admin<S2, E2> addStep(final int index, final Step<?, ?> step) throws IllegalStateException { |
| return (Traversal.Admin) this; |
| } |
| |
| @Override |
| public <S2, E2> Traversal.Admin<S2, E2> removeStep(final int index) throws IllegalStateException { |
| return (Traversal.Admin) this; |
| } |
| |
| @Override |
| public boolean equals(final Object object) { |
| return object instanceof EmptyTraversal; |
| } |
| |
| @Override |
| public int hashCode() { |
| return -343564565; |
| } |
| |
| @Override |
| public Set<TraverserRequirement> getTraverserRequirements() { |
| return Collections.emptySet(); |
| } |
| |
| @Override |
| public Optional<Graph> getGraph() { |
| return Optional.empty(); |
| } |
| |
| @Override |
| public void setGraph(final Graph graph) { |
| |
| } |
| } |