// renew.java
// system with growth based on renewable resources
// adapted from a program in basic by H.T. Odum & E. Odum, 1994

import java.applet.Applet;
import java.awt.*;

public class renew extends Applet {
  float k,k3,j,q,k4,jr,dq,q0;
	Label prompt1,prompt2;
	TextField input1,input2;
	public void init() {
	  prompt1 = new Label("Value for J (e.g. 45): ");
		input1 = new TextField(10);
		add(prompt1);add(input1);
		prompt2 = new Label("Q should start at (e.g. 1): ");
		input2 = new TextField(10);
		add(prompt2);add(input2);
	}
	public boolean action(Event e, Object o){

		j=(float)Integer.parseInt(input1.getText());
		q=(float)Integer.parseInt(input2.getText());
		repaint();

		return true;
	}
  public void paint ( Graphics g ){
	  int t,t0;
	  g.drawRect(0,60,320,240);

		q0=(float)0.1;t0=0;t=0;
		k=(float)0.1;
		k3=(float)8.000001e-03;
		k4=(float)0.03;
		while (t<=320){
		  jr=j/(1+k*q);
			dq=k3*jr*q-k4*q;
			q=q+dq;
			g.drawLine(t0, (int)(240-q0),t,(int)(240-q));
			t0=t;q0=q;
			t+=1;

		}
	}
}
// Stefan Kontur & e. Ortega. August 28th 2000