| /* |
| * 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.map; |
| |
| import org.apache.tinkerpop.gremlin.process.traversal.Traversal; |
| import org.apache.tinkerpop.gremlin.process.traversal.Traverser; |
| import org.apache.tinkerpop.gremlin.process.traversal.step.Seedable; |
| import org.apache.tinkerpop.gremlin.process.traversal.traverser.TraverserRequirement; |
| |
| import java.util.ArrayList; |
| import java.util.Collection; |
| import java.util.Collections; |
| import java.util.LinkedHashMap; |
| import java.util.List; |
| import java.util.Map; |
| import java.util.Random; |
| import java.util.Set; |
| |
| /** |
| * @author Daniel Kuppitz (http://gremlin.guru) |
| * @author Marko A. Rodriguez (http://markorodriguez.com) |
| */ |
| public final class SampleLocalStep<S> extends ScalarMapStep<S, S> implements Seedable { |
| |
| private final Random random = new Random(); |
| |
| private final int amountToSample; |
| |
| public SampleLocalStep(final Traversal.Admin traversal, final int amountToSample) { |
| super(traversal); |
| this.amountToSample = amountToSample; |
| } |
| |
| @Override |
| public void resetSeed(final long seed) { |
| this.random.setSeed(seed); |
| } |
| |
| @Override |
| protected S map(final Traverser.Admin<S> traverser) { |
| final S start = traverser.get(); |
| if (start instanceof Map) { |
| return mapMap((Map) start); |
| } else if (start instanceof Collection) { |
| return mapCollection((Collection) start); |
| } else { |
| return start; |
| } |
| } |
| |
| private S mapCollection(final Collection collection) { |
| if (collection.size() <= this.amountToSample) |
| return (S) collection; |
| |
| final List<S> original = new ArrayList<>(collection); |
| final List<S> target = new ArrayList<>(); |
| while (target.size() < this.amountToSample) { |
| target.add(original.remove(random.nextInt(original.size()))); |
| } |
| return (S) target; |
| } |
| |
| private S mapMap(final Map map) { |
| if (map.size() <= this.amountToSample) |
| return (S) map; |
| |
| final List<Map.Entry> original = new ArrayList<>(map.entrySet()); |
| final Map target = new LinkedHashMap<>(this.amountToSample); |
| while (target.size() < this.amountToSample) { |
| final Map.Entry entry = original.remove(random.nextInt(original.size())); |
| target.put(entry.getKey(), entry.getValue()); |
| } |
| return (S) target; |
| } |
| |
| @Override |
| public Set<TraverserRequirement> getRequirements() { |
| return Collections.singleton(TraverserRequirement.OBJECT); |
| } |
| |
| @Override |
| public int hashCode() { |
| return super.hashCode() ^ this.amountToSample; |
| } |
| } |