Java example source code file (LoopHelpers.java)

This example Java source code file (LoopHelpers.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

atomiclong, barriertimer, loophelpers, runnable, simplerandom, string, stringbuffer, threading, threads

The LoopHelpers.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/
 */

/**
 * Misc utilities in JSR166 performance tests
 */

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

class LoopHelpers {

    // Some mindless computation to do between synchronizations...

    /**
     * generates 32 bit pseudo-random numbers.
     * Adapted from http://www.snippets.org
     */
    public static int compute1(int x) {
        int lo = 16807 * (x & 0xFFFF);
        int hi = 16807 * (x >>> 16);
        lo += (hi & 0x7FFF) << 16;
        if ((lo & 0x80000000) != 0) {
            lo &= 0x7fffffff;
            ++lo;
        }
        lo += hi >>> 15;
        if (lo == 0 || (lo & 0x80000000) != 0) {
            lo &= 0x7fffffff;
            ++lo;
        }
        return lo;
    }

    /**
     *  Computes a linear congruential random number a random number
     *  of times.
     */
    public static int compute2(int x) {
        int loops = (x >>> 4) & 7;
        while (loops-- > 0) {
            x = (x * 2147483647) % 16807;
        }
        return x;
    }

    /**
     * An actually useful random number generator, but unsynchronized.
     * Basically same as java.util.Random.
     */
    public static class SimpleRandom {
        private static final long multiplier = 0x5DEECE66DL;
        private static final long addend = 0xBL;
        private static final long mask = (1L << 48) - 1;
        static final AtomicLong seq = new AtomicLong(1);
        private long seed = System.nanoTime() + seq.getAndIncrement();

        public void setSeed(long s) {
            seed = s;
        }

        public int next() {
            long nextseed = (seed * multiplier + addend) & mask;
            seed = nextseed;
            return ((int)(nextseed >>> 17)) & 0x7FFFFFFF;
        }
    }

    public static class BarrierTimer implements Runnable {
        public volatile long startTime;
        public volatile long endTime;
        public void run() {
            long t = System.nanoTime();
            if (startTime == 0)
                startTime = t;
            else
                endTime = t;
        }
        public void clear() {
            startTime = 0;
            endTime = 0;
        }
        public long getTime() {
            return endTime - startTime;
        }
    }

    public static String rightJustify(long n) {
        // There's probably a better way to do this...
        String field = "         ";
        String num = Long.toString(n);
        if (num.length() >= field.length())
            return num;
        StringBuffer b = new StringBuffer(field);
        b.replace(b.length()-num.length(), b.length(), num);
        return b.toString();
    }

}