import java.awt.*;

/** Copyright Will Wilson 1999
    birth-death simulation 

    @author Jeremy Harris
    @version 1.2
*/

public class bd
{
  public final int MAXTIME = 100;
  public final int PRNTTIME = 10;

  public bd(TextArea ta)
    /** the constructor for this object, initializes private 
	variables

	@param ta the textarea for the output of this program
    */
    {
      display = ta;
      nvals = new int[PRNTTIME];
    }
  
  public int[] GetNVals()
    /** gives an array of integers representing the values of n
	(the populations) that are printed to the textarea.
	
	@return nvals the array of n values
    */
    {      
      return nvals;
    }

  public void Start()
    /** begins running the simulation, clears the
	output area each time the sim is run
    */
    {
      display.setText("");
      int event;
      int n = 10;

      int index = 0;

      double alpha = 0.1;
      double beta = 0.1;
      
      display.append("time    pop\n  ");

      for(int ttt=0;ttt<MAXTIME;ttt++)
	{
	  event = 0;
	  if(Math.random()<alpha) event = 1;
	  if(Math.random()<beta) event = event - 1;
	  
	  n += event;
	  if(n<0)  n=0;
	  
	  if(ttt%PRNTTIME==0) 
	    {
	      display.append(" " + ttt + "    " + n + "\n");
	      nvals[index] = n;
	      index++;
	    }
	}		
    } 
 
  private TextArea display;
  private int[] nvals;
}