| /* |
| * 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.step.util; |
| |
| import org.apache.tinkerpop.gremlin.process.traversal.Step; |
| import org.apache.tinkerpop.gremlin.process.traversal.Traversal; |
| import org.apache.tinkerpop.gremlin.process.traversal.Traverser; |
| import org.apache.tinkerpop.gremlin.process.traversal.step.TraversalParent; |
| import org.apache.tinkerpop.gremlin.process.traversal.traverser.TraverserRequirement; |
| import org.apache.tinkerpop.gremlin.process.traversal.util.EmptyTraversal; |
| import org.apache.tinkerpop.gremlin.process.traversal.util.FastNoSuchElementException; |
| |
| import java.util.Collections; |
| import java.util.Iterator; |
| import java.util.Set; |
| |
| /** |
| * @author Marko A. Rodriguez (http://markorodriguez.com) |
| */ |
| public final class EmptyStep<S, E> implements Step<S, E>, TraversalParent { |
| |
| private static final EmptyStep INSTANCE = new EmptyStep<>(); |
| |
| public static <S, E> EmptyStep<S, E> instance() { |
| return INSTANCE; |
| } |
| |
| private EmptyStep() { |
| } |
| |
| @Override |
| public void addStarts(final Iterator<Traverser<S>> starts) { |
| |
| } |
| |
| @Override |
| public void addStart(final Traverser<S> start) { |
| |
| } |
| |
| @Override |
| public void setPreviousStep(final Step<?, S> step) { |
| |
| } |
| |
| @Override |
| public void reset() { |
| |
| } |
| |
| @Override |
| public Step<?, S> getPreviousStep() { |
| return INSTANCE; |
| } |
| |
| @Override |
| public void setNextStep(final Step<E, ?> step) { |
| |
| } |
| |
| @Override |
| public Step<E, ?> getNextStep() { |
| return INSTANCE; |
| } |
| |
| @Override |
| public <A, B> Traversal.Admin<A, B> getTraversal() { |
| return EmptyTraversal.instance(); |
| } |
| |
| @Override |
| public void setTraversal(final Traversal.Admin<?, ?> traversal) { |
| |
| } |
| |
| @Override |
| @SuppressWarnings("CloneDoesntCallSuperClone") |
| public EmptyStep<S, E> clone() { |
| return INSTANCE; |
| } |
| |
| @Override |
| public Set<String> getLabels() { |
| return Collections.emptySet(); |
| } |
| |
| @Override |
| public void addLabel(final String label) { |
| |
| } |
| |
| @Override |
| public void removeLabel(final String label) { |
| |
| } |
| |
| @Override |
| public void setId(final String id) { |
| |
| } |
| |
| @Override |
| public String getId() { |
| return Traverser.Admin.HALT; |
| } |
| |
| @Override |
| public boolean hasNext() { |
| return false; |
| } |
| |
| @Override |
| public Traverser<E> next() { |
| throw FastNoSuchElementException.instance(); |
| } |
| |
| @Override |
| public int hashCode() { |
| return -1691648095; |
| } |
| |
| @Override |
| public boolean equals(final Object object) { |
| return object instanceof EmptyStep; |
| } |
| |
| @Override |
| public Set<TraverserRequirement> getRequirements() { |
| return Collections.emptySet(); |
| } |
| } |