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Java example source code file (RacingCows.java)

This example Java source code file (RacingCows.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

assertionerror, checkedthread, copyonwritearraylist, copyonwritearrayset, integer, object, racingcows, some, thread, threading, threads, throwable, util

The RacingCows.java Java example source code

/*
 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

/*
 * @test
 * @bug 6330307 6355645
 * @summary Check for race conditions in COWArray classes
 * @author Martin Buchholz
 */

import java.util.*;
import java.util.concurrent.*;

public class RacingCows {
    private static void realMain(String[] args) throws Throwable {
        final int iterations = 100000;
        final Integer two = Integer.valueOf(2);
        final Integer three = Integer.valueOf(3);

        //------------ CopyOnWriteArraySet -------------------------------
        final Set<Integer> s1 = new CopyOnWriteArraySet();
        final Set<Integer> s2 = new CopyOnWriteArraySet();
        s1.add(1);

        final Thread t1 = new CheckedThread() { public void realRun() {
            for (int i = 0; i < iterations; i++) {
                s2.add(two);
                s2.remove(two);
            }}};
        t1.start();

        for (int i = 0; i < iterations; i++) {
            check(! s1.equals(s2));
            check(! s2.equals(s1));
        }
        t1.join();

        //------------ CopyOnWriteArrayList ------------------------------
        final List<Integer> l1 = new CopyOnWriteArrayList();
        final List<Integer> l2 = new CopyOnWriteArrayList();
        final List<Integer> l3 = new CopyOnWriteArrayList();
        l1.add(1);

        final Thread t2 = new CheckedThread() { public void realRun() {
            for (int i = 0; i < iterations; i++) {
                switch (i%2) {
                case 0: l2.add(two);    break;
                case 1: l2.add(0, two); break;
                }
                switch (i%3) {
                case 0: l2.remove(two); break;
                case 1: l2.remove(0);   break;
                case 2: l2.clear();     break;
                }}}};
        t2.start();

        final Thread t3 = new CheckedThread() { public void realRun() {
            l3.add(three);
            for (int i = 0; i < iterations; i++) {
                switch (i%2) {
                case 0: l3.add(two);    break;
                case 1: l3.add(0, two); break;
                }
                switch (i%2) {
                case 0: l3.remove(two); break;
                case 1: l3.remove(0);   break;
                }}}};
        t3.start();

        for (int i = 0; i < iterations; i++) {
            check(! l1.equals(l2));
            check(! l2.equals(l1));

            // CopyOnWriteArrayList(mutatingCollection)
            try { new CopyOnWriteArrayList<Integer>(l2); }
            catch (Throwable t) { unexpected(t); }

            // addAllAbsent(mutatingCollection)
            try { new CopyOnWriteArrayList<Integer>().addAllAbsent(l3); }
            catch (Throwable t) { unexpected(t); }

            // addAll(mutatingCollection)
            try { new CopyOnWriteArrayList<Integer>().addAll(l3); }
            catch (Throwable t) { unexpected(t); }

            // addAll(int, mutatingCollection)
            try { new CopyOnWriteArrayList<Integer>().addAll(0,l3); }
            catch (Throwable t) { unexpected(t); }
        }
        t2.join();
        t3.join();
    }

    //--------------------- Infrastructure ---------------------------
    static volatile int passed = 0, failed = 0;
    static void pass() {passed++;}
    static void fail() {failed++; Thread.dumpStack();}
    static void fail(String msg) {System.out.println(msg); fail();}
    static void unexpected(Throwable t) {failed++; t.printStackTrace();}
    static void check(boolean cond) {if (cond) pass(); else fail();}
    static void equal(Object x, Object y) {
        if (x == null ? y == null : x.equals(y)) pass();
        else fail(x + " not equal to " + y);}
    public static void main(String[] args) throws Throwable {
        try {realMain(args);} catch (Throwable t) {unexpected(t);}
        System.out.printf("%nPassed = %d, failed = %d%n%n", passed, failed);
        if (failed > 0) throw new AssertionError("Some tests failed");}
    private abstract static class CheckedThread extends Thread {
        public abstract void realRun() throws Throwable;
        public void run() {
            try { realRun(); } catch (Throwable t) { unexpected(t); }}}
}

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