// nonrenew.java
// growth based on a nonrenewable source
// adapted from a program in basic by H.T. Odum & E. Odum, 1994

import java.applet.Applet;
import java.awt.*;
public class nonrenew extends Applet {
  Label pr1,pr2,pr3,pr4;
	TextField in1,in2,in3,in4;
	float ee,q,k,k1,k4,dq,de,t,ti,qi,ei;
  public void init() {
	  pr1 = new Label("Initial amount of nonrenewable source: ");
		in1 = new TextField("160",4);
		add(pr1);add(in1);
		pr2 = new Label("Initial population (try 1 to 100): ");
		in2 = new TextField("1",4);
		add(pr2);add(in2);
		pr3 = new Label("Growth rate: ");
		in3 = new TextField("10",4);
		add(pr3);add(in3);
		pr4 = new Label("Death rate: ");
		in4 = new TextField("3",4);
		add(pr4);add(in4);
	}
	public boolean action (Event e, Object o){
	  ee = (float)Integer.parseInt(in1.getText());
		q = 0.1f*(float)Integer.parseInt(in2.getText());
		k1 = 0.0001f*(float)Integer.parseInt(in3.getText());
		k4 = 0.01f*(float)Integer.parseInt(in4.getText());
		repaint();
		return true;
	}
	public void paint (Graphics g){
	  k=0.001f;qi=q;ei=ee;t=0;ti=t;
		g.drawRect(60,150,320,180);
		while (t<320) {
		  dq=ee*k1*q-k4*q;
			de=-k*ee*q;
			q+=dq;
			ee+=de;
			t+=1;
			g.setColor(Color.red);
			g.drawLine((int)(60+ti),(int)(330-qi),(int)(60+t),(int)(330-q));
			g.setColor(Color.blue);
			g.drawLine((int)(60+ti),(int)(330-ei),(int)(60+t),(int)(330-ee));
			qi=q;ei=ee;ti=t;
		}
	}
}
// Stefan Kontur & E. Ortega, August 30th 2000