Java example source code file (Basic.java)

This example Java source code file (Basic.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

arriver, assertionerror, atomicinteger, awaiter, error, interruptiblewaiter, iterator, linkedlist, phaser, seconds, some, threading, threads, throwable, timeunit, unsupportedoperationexception, util

The Basic.java Java example source code

/*
 * 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.
 */

/*
 * This file is available under and governed by the GNU General Public
 * License version 2 only, as published by the Free Software Foundation.
 * However, the following notice accompanied the original version of this
 * file:
 *
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 */

/*
 * @test
 * @bug 6445158
 * @summary Basic tests for Phaser
 * @author Chris Hegarty
 */

import java.util.Iterator;
import java.util.LinkedList;
import java.util.concurrent.Phaser;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicInteger;
import static java.util.concurrent.TimeUnit.*;

public class Basic {

    private static void checkTerminated(final Phaser phaser) {
        check(phaser.isTerminated());
        int unarriverParties = phaser.getUnarrivedParties();
        int registeredParties = phaser.getRegisteredParties();
        int phase = phaser.getPhase();
        check(phase < 0);
        equal(phase, phaser.arrive());
        equal(phase, phaser.arriveAndDeregister());
        equal(phase, phaser.arriveAndAwaitAdvance());
        equal(phase, phaser.bulkRegister(10));
        equal(phase, phaser.register());
        try {
            equal(phase, phaser.awaitAdvanceInterruptibly(0));
            equal(phase, phaser.awaitAdvanceInterruptibly(0, 10, SECONDS));
        } catch (Exception ie) {
            unexpected(ie);
        }
        equal(phaser.getUnarrivedParties(), unarriverParties);
        equal(phaser.getRegisteredParties(), registeredParties);
    }

    private static void checkResult(Arriver a, Class<? extends Throwable> c) {
        Throwable t = a.result();
        if (! ((t == null && c == null) || (c != null && c.isInstance(t)))) {
            //      t.printStackTrace();
            fail("Mismatch in thread " +
                 a.getName() + ": " +
                 t + ", " +
                 (c == null ? "<null>" : c.getName()));
        } else {
            pass();
        }
    }

    //----------------------------------------------------------------
    // Mechanism to get all test threads into "running" mode.
    //----------------------------------------------------------------
    private static Phaser atTheStartingGate = new Phaser(3);

    private static void toTheStartingGate() {
        try {
            boolean expectNextPhase = false;
            if (atTheStartingGate.getUnarrivedParties() == 1) {
                expectNextPhase = true;
            }
            int phase = atTheStartingGate.getPhase();
            equal(phase, atTheStartingGate.arrive());
            int awaitPhase = atTheStartingGate.awaitAdvanceInterruptibly
                (phase, 30, SECONDS);
            if (expectNextPhase) check(awaitPhase == (phase + 1));

            pass();
        } catch (Throwable t) {
            unexpected(t);
           // reset(atTheStartingGate);
            throw new Error(t);
        }
    }

    //----------------------------------------------------------------
    // Convenience methods for creating threads that call arrive,
    // awaitAdvance, arriveAndAwaitAdvance, awaitAdvanceInterruptibly
    //----------------------------------------------------------------
    private static abstract class Arriver extends Thread {
        static AtomicInteger count = new AtomicInteger(1);

        Arriver() {
            this("Arriver");
        }

        Arriver(String name) {
            this.setName(name + ":" + count.getAndIncrement());
            this.setDaemon(true);
        }

        private volatile Throwable result;
        private volatile int phase;
        protected void result(Throwable result) { this.result = result; }
        public Throwable result() { return this.result; }
        protected void phase(int phase) { this.phase = phase; }
        public int phase() { return this.phase; }
    }

    private static abstract class Awaiter extends Arriver {
        Awaiter() { super("Awaiter"); }
        Awaiter(String name) { super(name); }
    }

    private static Arriver arriver(final Phaser phaser) {
        return new Arriver() { public void run() {
            toTheStartingGate();

            try { phase(phaser.arrive()); }
            catch (Throwable result) { result(result); }}};
    }

    private static AtomicInteger cycleArriveAwaitAdvance = new AtomicInteger(1);

    private static Awaiter awaiter(final Phaser phaser) {
        return new Awaiter() { public void run() {
            toTheStartingGate();

            try {
                if (cycleArriveAwaitAdvance.getAndIncrement() % 2 == 0)
                    phase(phaser.awaitAdvance(phaser.arrive()));
                else
                    phase(phaser.arriveAndAwaitAdvance());
            } catch (Throwable result) { result(result); }}};
    }

    private static Awaiter awaiter(final Phaser phaser,
                                   final long timeout,
                                   final TimeUnit unit) {
        return new Awaiter("InterruptibleWaiter") { public void run() {
            toTheStartingGate();

            try {
                if (timeout < 0)
                    phase(phaser.awaitAdvanceInterruptibly(phaser.arrive()));
                else
                    phase(phaser.awaitAdvanceInterruptibly(phaser.arrive(),
                                                     timeout,
                                                     unit));
            } catch (Throwable result) { result(result); }}};
    }

    // Returns an infinite lazy list of all possible arriver/awaiter combinations.
    private static Iterator<Arriver> arriverIterator(final Phaser phaser) {
        return new Iterator<Arriver>() {
            int i = 0;
            public boolean hasNext() { return true; }
            public Arriver next() {
                switch ((i++)&7) {
                    case 0: case 4:
                        return arriver(phaser);
                    case 1: case 5:
                        return awaiter(phaser);
                    case 2: case 6: case 7:
                        return awaiter(phaser, -1, SECONDS);
                    default:
                        return awaiter(phaser, 30, SECONDS); }}
            public void remove() {throw new UnsupportedOperationException();}};
    }

    // Returns an infinite lazy list of all possible awaiter only combinations.
    private static Iterator<Awaiter> awaiterIterator(final Phaser phaser) {
        return new Iterator<Awaiter>() {
            int i = 0;
            public boolean hasNext() { return true; }
            public Awaiter next() {
                switch ((i++)&7) {
                    case 1: case 4: case 7:
                        return awaiter(phaser);
                    case 2: case 5:
                        return awaiter(phaser, -1, SECONDS);
                    default:
                        return awaiter(phaser, 30, SECONDS); }}
            public void remove() {throw new UnsupportedOperationException();}};
    }

    private static void realMain(String[] args) throws Throwable {

        Thread.currentThread().setName("mainThread");

        //----------------------------------------------------------------
        // Normal use
        //----------------------------------------------------------------
        try {
            Phaser phaser = new Phaser(3);
            equal(phaser.getRegisteredParties(), 3);
            equal(phaser.getArrivedParties(), 0);
            equal(phaser.getPhase(), 0);
            check(phaser.getRoot().equals(phaser));
            equal(phaser.getParent(), null);
            check(!phaser.isTerminated());

            Iterator<Arriver> arrivers = arriverIterator(phaser);
            int phase = 0;
            for (int i = 0; i < 10; i++) {
                equal(phaser.getPhase(), phase++);
                Arriver a1 = arrivers.next(); a1.start();
                Arriver a2 = arrivers.next(); a2.start();
                toTheStartingGate();
                phaser.arriveAndAwaitAdvance();
                a1.join();
                a2.join();
                checkResult(a1, null);
                checkResult(a2, null);
                check(!phaser.isTerminated());
                equal(phaser.getRegisteredParties(), 3);
                equal(phaser.getArrivedParties(), 0);
            }
        } catch (Throwable t) { unexpected(t); }

        //----------------------------------------------------------------
        // One thread interrupted
        //----------------------------------------------------------------
        try {
            Phaser phaser = new Phaser(3);
            Iterator<Arriver> arrivers = arriverIterator(phaser);
            int phase = phaser.getPhase();
            for (int i = 0; i < 4; i++) {
                check(phaser.getPhase() == phase);
                Awaiter a1 = awaiter(phaser, 30, SECONDS); a1.start();
                Arriver a2 = arrivers.next(); a2.start();
                toTheStartingGate();
                // allow a1 to block in awaitAdvanceInterruptibly
                Thread.sleep(2000);
                a1.interrupt();
                a1.join();
                phaser.arriveAndAwaitAdvance();
                a2.join();
                checkResult(a1, InterruptedException.class);
                checkResult(a2, null);
                check(!phaser.isTerminated());
                equal(phaser.getRegisteredParties(), 3);
                equal(phaser.getArrivedParties(), 0);
                phase++;
            }
        } catch (Throwable t) { unexpected(t); }

        //----------------------------------------------------------------
        // Phaser is terminated while threads are waiting
        //----------------------------------------------------------------
        try {
            for (int i = 0; i < 4; i++) {
                Phaser phaser = new Phaser(3);
                Iterator<Awaiter> awaiters = awaiterIterator(phaser);
                Arriver a1 = awaiters.next(); a1.start();
                Arriver a2 = awaiters.next(); a2.start();
                toTheStartingGate();
                while (phaser.getArrivedParties() < 2) Thread.yield();
                equal(0, phaser.getPhase());
                phaser.forceTermination();
                a1.join();
                a2.join();
                equal(0 + Integer.MIN_VALUE, a1.phase);
                equal(0 + Integer.MIN_VALUE, a2.phase);
                int arrivedParties = phaser.getArrivedParties();
                checkTerminated(phaser);
                equal(phaser.getArrivedParties(), arrivedParties);
            }
        } catch (Throwable t) { unexpected(t); }

        //----------------------------------------------------------------
        // Adds new unarrived parties to this phaser
        //----------------------------------------------------------------
        try {
            Phaser phaser = new Phaser(1);
            Iterator<Arriver> arrivers = arriverIterator(phaser);
            LinkedList<Arriver> arriverList = new LinkedList();
            int phase = phaser.getPhase();
            for (int i = 1; i < 5; i++) {
                atTheStartingGate = new Phaser(1+(3*i));
                check(phaser.getPhase() == phase);
                // register 3 more
                phaser.register(); phaser.register(); phaser.register();
                for (int z=0; z<(3*i); z++) {
                   arriverList.add(arrivers.next());
                }
                for (Arriver arriver : arriverList)
                    arriver.start();

                toTheStartingGate();
                phaser.arriveAndAwaitAdvance();

                for (Arriver arriver : arriverList) {
                    arriver.join();
                    checkResult(arriver, null);
                }
                equal(phaser.getRegisteredParties(), 1 + (3*i));
                equal(phaser.getArrivedParties(), 0);
                arriverList.clear();
                phase++;
            }
            atTheStartingGate = new Phaser(3);
        } catch (Throwable t) { unexpected(t); }

        //----------------------------------------------------------------
        // One thread timed out
        //----------------------------------------------------------------
        try {
            Phaser phaser = new Phaser(3);
            Iterator<Arriver> arrivers = arriverIterator(phaser);
            for (long timeout : new long[] { 0L, 5L }) {
                for (int i = 0; i < 2; i++) {
                    Awaiter a1 = awaiter(phaser, timeout, SECONDS); a1.start();
                    Arriver a2 = arrivers.next();                   a2.start();
                    toTheStartingGate();
                    a1.join();
                    checkResult(a1, TimeoutException.class);
                    phaser.arrive();
                    a2.join();
                    checkResult(a2, null);
                    check(!phaser.isTerminated());
                }
            }
        } catch (Throwable t) { unexpected(t); }

        //----------------------------------------------------------------
        // Barrier action completed normally
        //----------------------------------------------------------------
        try {
            final AtomicInteger count = new AtomicInteger(0);
            final Phaser[] kludge = new Phaser[1];
            Phaser phaser = new Phaser(3) {
                @Override
                protected boolean onAdvance(int phase, int registeredParties) {
                    int countPhase = count.getAndIncrement();
                    equal(countPhase, phase);
                    equal(kludge[0].getPhase(), phase);
                    equal(kludge[0].getRegisteredParties(), registeredParties);
                    if (phase >= 3)
                        return true; // terminate

                    return false;
                }
            };
            kludge[0] = phaser;
            equal(phaser.getRegisteredParties(), 3);
            Iterator<Awaiter> awaiters = awaiterIterator(phaser);
            for (int i = 0; i < 4; i++) {
                Awaiter a1 = awaiters.next(); a1.start();
                Awaiter a2 = awaiters.next(); a2.start();
                toTheStartingGate();
                while (phaser.getArrivedParties() < 2) Thread.yield();
                phaser.arrive();
                a1.join();
                a2.join();
                checkResult(a1, null);
                checkResult(a2, null);
                equal(count.get(), i+1);
                if (i < 3) {
                    check(!phaser.isTerminated());
                    equal(phaser.getRegisteredParties(), 3);
                    equal(phaser.getArrivedParties(), 0);
                    equal(phaser.getUnarrivedParties(), 3);
                    equal(phaser.getPhase(), count.get());
                } else
                    checkTerminated(phaser);
            }
        } catch (Throwable t) { unexpected(t); }

    }

    //--------------------- 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");}
}