// File: random_example2.java
//
// Author: Rahul Simha
// Created: Sept 5, 2000
//

public class random_example2 {
  // Basic Lehmer generator - constants
  static final long m = 2147483647L;
  static final long a = 48271L;
  static final long q = 44488L;
  static final long r = 3399L;

  // "Global" variable - the seed, set to some 
  // arbitrary non-zero value.
  static long r_seed = 12345678L; 

  // Basic Lehmer generator - uniform[0,1]
  // For more information see Knuth, Vol. II.
  public static double uniform ()
  {
    long hi = r_seed / q;
    long lo = r_seed - q * hi;
    long t = a * lo - r * hi;
    if (t > 0)
      r_seed = t;
    else
      r_seed = t + m;
    return ( (double) r_seed / (double) m );
  }

  public static void main (String[] argv)
  {
    double[] A = new double [5];
    int numArrays = 10000;
    int numOccurences = 0;

    for (int n=1; n<=numArrays; n++) {
      // Generate random values.
      for (int i=0; i<5; i++) 
        A[i] = uniform();

      // Check for property.
      boolean property = true;
      for (int i=1; i<5; i++) {
        if (A[i] < A[i-1])
          property = false;
      }

      // Count.
      if (property)
        numOccurences++;
    }
    
    // Now estimate probability
    double prob = (double) numOccurences / (double) numArrays;
    System.out.println ("Probability estimate: " + prob);
  }

}