The Dragon Curve

/*
 * Author: Daniel Tanner
 * Dragon Curve Program
 *
 * This program runs a recursive program to keep replacing a given
 * string such as "f" with "f+h" and "h" with "f-h",
 *  and after a certain number of said recursions, translates that
 *  string into a physical display.  The result is known as the
 *  Dragon Curve.
 */

import java.awt.*;
import java.util.Random;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class DragonCurve extends JPanel {
 
 public Graphics g1;
 public Color c =Color.WHITE; // set colour to white to create the blanks
 public Random r = new Random();

 public static double degToRad(int deg) { //degree to radian conversion
  return deg * Math.PI / 180;
 }


 //paint method is automatically called for us by tree recursive (will be called 4 times! Once for each call to drawFractal
 public void paint(final Graphics g) {
  this.g1 = g;
  g1.setColor(c);
  int numRecursions = 14;
  double startAngle = degToRad(0);
  int distance = 3;
   //First call to do the drawing, this call draws the trunk: start(X,Y) at base, angle 0, len calculated)
  drawCurve(getWidth() / 2, getHeight() / 2, numRecursions, startAngle, distance);  //first call
     //System.out.println("in paint, number of calls to drawFractal is " + count +"\n");
   }

 //dragon curve method -- starts at the middle and applies rules to curve
 public void drawCurve(int x0, int y0, int numRecursions, double startAngle, int distance)
 {
    String dragonString = "f";
    for(int i = 0; i < numRecursions; i++)
    {
        String tempString = "";
        for(int j = 0; j < dragonString.length(); j++)
        {    //replace the f with f + h
            if(dragonString.charAt(j) == 'f')
                tempString += "f-h";
            else if(dragonString.charAt(j) == 'h')
                tempString += "f+h";
            else
                tempString += dragonString.charAt(j);
        }
        dragonString = tempString;
    }
    System.out.println(dragonString);
    //now draw the image
    for(int index = 0; index < dragonString.length(); index++)
    {
        if(dragonString.charAt(index) == 'f' || dragonString.charAt(index) == 'h')
        {
            g1.setColor(new Color((int)(Math.random() * 255), (int)(Math.random() * 255), (int)(Math.random() * 255)));          //random colour (default is white)
            int x1 = (int)(x0 + distance * Math.cos(startAngle));
            int y1 = (int)(y0 + distance * Math.sin(startAngle));
            g1.drawLine(x0, y0, x1, y1);
            x0 = x1; y0 = y1;
        }
        else if(dragonString.charAt(index) == 'g')
        {
            g1.setColor(new Color((int)(Math.random() * 255), (int)(Math.random() * 255), (int)(Math.random() * 255)));          //random colour (default is white)
            int x1 = (int)(x0 + distance * Math.cos(startAngle));
            int y1 = (int)(y0 + distance * Math.sin(startAngle));
            x0 = x1; y0 = y1;
        }
        else if(dragonString.charAt(index) == '+')
            startAngle = startAngle - Math.PI / 2.0;
        else if(dragonString.charAt(index) == '-')
            startAngle = startAngle + Math.PI / 2.0;
    }
 }

 //main method
 public static void main(String args[]) {
   // System.out.println("count begins with at " + count +"\n");
  JFrame FF = new JFrame("Drawing the Dragon Curve");
  FF.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  FF.setVisible(true);   //Show the first drawing.
  DragonCurve F = new DragonCurve();  //call default constructor (not written); F is the Tree.
  FF.setBackground(Color.BLACK);
  FF.add(F);
  FF.setSize(1000, 1000);  //(width 1200,height 1000)   
 }
}