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Java example source code file (IteratorBenchmark.java)

This example Java source code file (IteratorBenchmark.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

arraylist, beforeexperiment, benchmark, iteratorbenchmark, linkedlist, object, param, util

The IteratorBenchmark.java Java example source code

/*
 * Copyright (C) 2010 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.collect;

import com.google.caliper.BeforeExperiment;
import com.google.caliper.Benchmark;
import com.google.caliper.Param;

import java.util.ArrayList;
import java.util.LinkedList;

/**
 * Tests the speed of iteration of different iteration methods for collections.
 *
 * @author David Richter
 */
public class IteratorBenchmark {
  @Param({"0", "1", "16", "256", "4096", "65536"}) int size;

  // use concrete classes to remove any possible polymorphic overhead?
  Object[] array;
  ArrayList<Object> arrayList;
  LinkedList<Object> linkedList;

  @BeforeExperiment void setUp() {
    array = new Object[size];
    arrayList = Lists.newArrayListWithCapacity(size);
    linkedList = Lists.newLinkedList();

    for (int i = 0; i < size; i++) {
      Object value = new Object();
      array[i] = value;
      arrayList.add(value);
      linkedList.add(value);
    }
  }

  @Benchmark int arrayIndexed(int reps) {
    int sum = 0;
    for (int i = 0; i < reps; i++) {
      for (int index = 0; index < size; index++) {
        sum += array[index].hashCode();
      }
    }
    return sum;
  }

  @Benchmark int arrayIndexedLength(int reps) {
    int sum = 0;
    for (int i = 0; i < reps; i++) {
      for (int index = 0; index < array.length; index++) {
        sum += array[index].hashCode();
      }
    }
    return sum;
  }

  @Benchmark int arrayFor(int reps) {
    int sum = 0;
    for (int i = 0; i < reps; i++) {
      for (Object value : array) {
        sum += value.hashCode();
      }
    }
    return sum;
  }

  @Benchmark int arrayListIndexed(int reps) {
    int sum = 0;
    for (int i = 0; i < reps; i++) {
      for (int index = 0; index < size; index++) {
        sum += arrayList.get(index).hashCode();
      }
    }
    return sum;
  }

  @Benchmark int arrayListIndexedLength(int reps) {
    int sum = 0;
    for (int i = 0; i < reps; i++) {
      for (int index = 0; index < arrayList.size(); index++) {
        sum += arrayList.get(index).hashCode();
      }
    }
    return sum;
  }

  @Benchmark int arrayListFor(int reps) {
    int sum = 0;
    for (int i = 0; i < reps; i++) {
      for (Object value : arrayList) {
        sum += value.hashCode();
      }
    }
    return sum;
  }

  @Benchmark int arrayListToArrayFor(int reps) {
    int sum = 0;
    for (int i = 0; i < reps; i++) {
      for (Object value : arrayList.toArray()) {
        sum += value.hashCode();
      }
    }
    return sum;
  }

  @Benchmark int linkedListFor(int reps) {
    int sum = 0;
    for (int i = 0; i < reps; i++) {
      for (Object value : linkedList) {
        sum += value.hashCode();
      }
    }
    return sum;
  }

  @Benchmark int linkedListToArrayFor(int reps) {
    int sum = 0;
    for (int i = 0; i < reps; i++) {
      for (Object value : linkedList.toArray()) {
        sum += value.hashCode();
      }
    }
    return sum;
  }
}

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