// This program is a working example of a java program that can draw some 
// simple graphics.  You can use it as a template but at least change the 
// class name and the drawstuff method name to something else.

import java.awt.*;
import java.awt.Graphics;
import javax.swing.*;

public class tri17 extends JFrame
{
    private int width;  // dimensions of window in pixels
    private int height;
    private Graphics display; // drawing object

    // constructor
    public tri17(int x, int y)// x,y indicate width, height
    { width=x; height=y;
      this.setBounds(0,0,width,height);
      setVisible(true);
      this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      display = this.getGraphics();  // drawing object
      display.setColor(Color.white);
      display.fillRect(0,0,width,height); // draw solid white rectangle
      try { Thread.sleep(500); } catch (Exception e) {} // synch with system

      //      trianglel(); // call user function that draws
      display.setColor(Color.blue);
      int x1= width/2, y1 = 40;
      int x2= 20, y2=height-20;
      int x3 = width-20, y3= height-20;
      triangle(x1,y1,x2,y2,x3,y3);
    }

    // whith recursion
    protected void triangle(int x1,int y1,int x2,int y2,int x3, int y3)
    {
	      display.drawLine(x1,y1,x2,y2);
	      display.drawLine(x2,y2,x3,y3);
	      display.drawLine(x1,y1,x3,y3);
	      	try { Thread.sleep(10); } catch (Exception e) {}
	      if (Math.abs(x2-x3)>=4) // continue?
		  {
		      // compute midpoints:
		      int lx = (x1+x2)/2, ly = (y1+y2)/2;
		      int rx = (x1+x3)/2, ry = (y1+y3)/2;
		      int bx = (x2+x3)/2, by = (y2+y3)/2;
		      // make 3 recursive calls
		      triangle(x1,y1,lx,ly,rx,ry);
		      triangle(lx,ly,x2,y2,bx,by);
		      triangle(rx,ry,bx,by,x3,y3);
		  }// if continue	
    }// why is this a safe use of recursion?

    // "without" recursion
    protected void trianglel()
    {
      display.setColor(Color.blue);
      int x1= width/2, y1 = 40;
      int x2= 20, y2=height-20;
      int x3 = width-20, y3= height-20;
      // draw three lines of triangle
      LinkedList<tinfo> Stack = new LinkedList<tinfo>(); // see LinkedList.java
      Stack.push(new tinfo(x1,y1,x2,y2,x3,y3));
      
      while (Stack.size()>0)
	  {
	      // pop stack:
	      tinfo tf = Stack.pop();
	      x1= tf.x1; y1=tf.y1; // load into convenient vars
	      x2= tf.x2; y2=tf.y2;
	      x3= tf.x3; y3=tf.y3;
	      display.drawLine(x1,y1,x2,y2);
	      display.drawLine(x2,y2,x3,y3);
	      display.drawLine(x1,y1,x3,y3);
	      //	      try { Thread.sleep(10); } catch (Exception e) {}
	      if (Math.abs(x2-x3)>=4) // continue?
		  {
		      // compute midpoints:
		      int lx = (x1+x2)/2, ly = (y1+y2)/2;
		      int rx = (x1+x3)/2, ry = (y1+y3)/2;
		      int bx = (x2+x3)/2, by = (y2+y3)/2;
		      // push three frames on stack
		      Stack.push(new tinfo(x1,y1,lx,ly,rx,ry));
		      Stack.push(new tinfo(lx,ly,x2,y2,bx,by));
		      Stack.push(new tinfo(rx,ry,bx,by,x3,y3));
		  }// if continue
	  }//main recursion loop
    }// user-defined drawing function

    // the following method is called when the window needs to be repainted:
    public void paint(Graphics g) { } // override autopaint method


    // main must create an instance of tri17 class:
    public static void main(String[] args)
    {
	tri17 t = new tri17(800,700); // create instance
    }


    class tinfo // internal class for one triangle
    {
	int x1, x2, x3, y1, y2, y3;
	public tinfo(int a, int b, int c, int d, int e, int f)
	{
	    x1=a; y1 = b;
	    x2=c; y2=d;
	    x3 =e; y3=f;
	}
    }//tinfo  for stack frames
    
    
}//tri17