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Java example source code file (

This example Java source code file ( is included in the "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, callable, collectionholder, copyonwritearraylist, executionexception, executorservice, integer, interruptedexception, list, list_size, override, repeat, test, threading, threads, tostringstyleconcurrencytest, util

The Java example source code

 * 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
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the License for the specific language governing permissions and
 * limitations under the License.

package org.apache.commons.lang3.builder;

import java.util.ArrayList;
import java.util.Collection;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;

import org.junit.Test;

 * Tests concurrent access for the default {@link ToStringStyle}.
 * <p>
 * The {@link ToStringStyle} class includes a registry to avoid infinite loops for objects with circular references. We
 * want to make sure that we do not get concurrency exceptions accessing this registry.
 * </p>
 * <p>
 * This test passes but only tests one aspect of the issue.
 * </p>
 * @see <a href="">[LANG-762] Handle or document ReflectionToStringBuilder
 *      and ToStringBuilder for collections that are not thread safe</a>
 * @since 3.1
public class ToStringStyleConcurrencyTest {

    static class CollectionHolder<T extends Collection {
        T collection;

        CollectionHolder(final T collection) {
            this.collection = collection;

    private static final List<Integer> LIST;
    private static final int LIST_SIZE = 100000;
    private static final int REPEAT = 100;

    static {
        LIST = new ArrayList<Integer>(LIST_SIZE);
        for (int i = 0; i < LIST_SIZE; i++) {

    public void testLinkedList() throws InterruptedException, ExecutionException {
        this.testConcurrency(new CollectionHolder<List(new LinkedList()));

    public void testArrayList() throws InterruptedException, ExecutionException {
        this.testConcurrency(new CollectionHolder<List(new ArrayList()));

    public void testCopyOnWriteArrayList() throws InterruptedException, ExecutionException {
        this.testConcurrency(new CollectionHolder<List(new CopyOnWriteArrayList()));

    private void testConcurrency(final CollectionHolder<List holder) throws InterruptedException,
            ExecutionException {
        final List<Integer> list = holder.collection;
        // make a big array that takes a long time to toString()
        // Create a thread pool with two threads to cause the most contention on the underlying resource.
        final ExecutorService threadPool = Executors.newFixedThreadPool(2);
        // Consumes toStrings
        final Callable<Integer> consumer = new Callable() {
            public Integer call() {
                for (int i = 0; i < REPEAT; i++) {
                    // Calls ToStringStyle
                    new ToStringBuilder(holder).append(holder.collection);
                return Integer.valueOf(REPEAT);
        final Collection<Callable tasks = new ArrayList>();
        final List<Future futures = threadPool.invokeAll(tasks);
        for (final Future<Integer> future : futures) {
        threadPool.awaitTermination(1, TimeUnit.SECONDS);

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