code: // from gee.cs.oswego.edu/home/jsr166/jsr166
  
  package jsr166tests.jtreg.util.concurrent.locks.Lock;
  
  /*
   * 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/licenses/publicdomain
   */
  
  /**
   * 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 final static long multiplier = 0x5DEECE66DL;
          private final static long addend = 0xBL;
          private final static 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();
      }
  
  }
  