/* From: "COMPUTATIONAL PHYSICS, 2nd Ed" 
   by RH Landau, MJ Paez, and CC Bordeianu 
   Copyright Wiley-VCH, 2007.
   Electronic Materials copyright: R Landau, Oregon State Univ, 2007;
   MJ Paez, Univ Antioquia, 2007; and CC Bordeianu, Univ Bucharest, 2007.
   Support by National Science Foundation                              
*/
// Decay.java: Spontaneous decay simulation 

import java.io.*; 
import java.util.*;
                 
public class Decay {
  static double lambda = 0.01;                      // Decay constant
  static int max = 1000, time_max = 500, seed = 68111;      // Params
   
  public static void main(String[] argv) 
                     throws IOException, FileNotFoundException {
											 
    int atom, time, number, nloop; 
    double decay; 
		
    PrintWriter w = 
        new PrintWriter(new FileOutputStream("decay.dat"), true); 
    number = nloop = max;                            // Initial value
    Random r = new Random(seed);             // Seed random generator
		                                                     // Time loop
    for ( time = 0;  time <= time_max;  time++ ) {            
			                                                   // Atom loop
      for ( atom = 1;  atom <= number;  atom++ )  {           
        decay = r.nextDouble(); 
        if (decay  <  lambda) nloop--;  
      }                                             // An atom decays
      number = nloop; 
      w.println( " " + time + "  " + (double)number/max); 
    }
   System.out.println("data stored in decay.dat"); 
  } 
}