/*

 * Cay S. Horstmann & Gary Cornell, Core Java

 * Published By Sun Microsystems Press/Prentice-Hall

 * Copyright (C) 1997 Sun Microsystems Inc.

 * All Rights Reserved.

 *

 * Permission to use, copy, modify, and distribute this 

 * software and its documentation for NON-COMMERCIAL purposes

 * and without fee is hereby granted provided that this 

 * copyright notice appears in all copies. 

 * 

 * THE AUTHORS AND PUBLISHER MAKE NO REPRESENTATIONS OR 

 * WARRANTIES ABOUT THE SUITABILITY OF THE SOFTWARE, EITHER 

 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE 

 * IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A 

 * PARTICULAR PURPOSE, OR NON-INFRINGEMENT. THE AUTHORS

 * AND PUBLISHER SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED 

 * BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING 

 * THIS SOFTWARE OR ITS DERIVATIVES.

 */

 

/**

 * an improved random number generator based on Algorithm B

 * in Knuth Vol 2 p32

 * gives a range of random integers that do not exhibit

 * as much correlation as the method used in Java

 * @version 1.01 15 Feb 1996 

 * @author Cay Horstmann

 */



package corejava;



public class RandomIntGenerator

{  /** Constructs the class that encapsulates the random integer  

   * @param l the lowest integer in the range

   * @param h the highest integer in the range

   */



   public RandomIntGenerator(int l, int h)

   {  low = l;

      high = h;

   }

   

   /** 

   * Used to return a random integer in the range constructed

   */

   

   public int draw()

   {  int r = low 

         + (int)((high - low + 1) * nextRandom());

      if (r > high) r = high;

      return r;

   }



   /**

   * test stub for the class

   */

   

   public static void main(String[] args)

   {  RandomIntGenerator r1 

         = new RandomIntGenerator(1, 10);

      RandomIntGenerator r2 

         = new RandomIntGenerator(0, 1);

      int i;

      for (i = 1; i <= 100; i++)

         System.out.println(r1.draw() + " " + r2.draw());

   }



   private static double nextRandom()

   {  int pos = 

         (int)(java.lang.Math.random() * BUFFER_SIZE);

      if (pos == BUFFER_SIZE) pos = BUFFER_SIZE - 1;

      double r = buffer[pos];

      buffer[pos] = java.lang.Math.random();

      return r;

   }

   

   private static final int BUFFER_SIZE = 101;

   private static double[] buffer 

      = new double[BUFFER_SIZE];

   static 

   {  int i;

      for (i = 0; i < BUFFER_SIZE; i++)

         buffer[i] = java.lang.Math.random();

   }

   

   private int low;

   private int high;

}