Joining lines & saving co-ordinates!

Question

Well, I did manage to do something with my problem (posted last night) but here's another question.
I'll start again for those new to this...
I'm writing a 'sketch pad' program where the user draws 3 seperate lines (not touching) and then I have to extend them to make a decent looking triangle! Well, for now I've managed to get a canvas up and allow the user to draw lines.
Anyone got any ideas/tips on how to join the lines up, or just to save the co-ordinates (startx, starty, endx & endy) of each line in an array (so that I can repaint the canvas when it is put behind another window!)?
Here's the code I've done so far;
Sketcher.java
import java.awt.*;
import java.awt.event.*;
public class Sketcher extends Frame {
     private Canvas canvas;
     public Sketcher() {
          setSize(500, 500);
          setTitle("Sketch Pad");
          canvas = new Canvas();
          add(canvas, "Center");
    public static void main(String[] args) {
          Sketcher f = new Sketcher();
          MouseWatcher mw = new MouseWatcher();
          f.canvas.addMouseListener(mw);
          f.canvas.addMouseMotionListener(mw);
          f.show();
MouseWatcher.java
import java.awt.*;
import java.awt.event.*;
public class MouseWatcher extends MouseAdapter implements MouseMotionListener {
     private Point p, oldp;
     public void mousePressed(MouseEvent e) {
          oldp = e.getPoint();
     public void mouseReleased(MouseEvent e) {
          p = e.getPoint();
          Graphics g = ((Canvas)e.getSource()).getGraphics();
          g.drawLine(oldp.x, oldp.y, p.x, p.y);
          oldp = p;
          g.dispose();
     public void mouseDragged(MouseEvent e) {
     public void mouseMoved(MouseEvent e) {
}Any help greatly appreciated... duke dollars available too, heh!

Answer 1

Was bored......
Havnt tried this but see if it works
  private Point p, oldp;
  private Point[] pts = new Point[6];
  int ctr = 0;
  int x1[] = new int[3];
  int y1[] = new int[3];
  int x2[] = new int[3];
  int y2[] = new int[3];
  public void mousePressed(MouseEvent e) {
    oldp = e.getPoint();
    x1[ctr] = (int)oldp.getX();
    y1[ctr] = (int)oldp.getY();
  public void mouseReleased(MouseEvent e) {
    p = e.getPoint();
    Graphics g = ( (Canvas) e.getSource()).getGraphics();
    g.drawLine(oldp.x, oldp.y, p.x, p.y);
    x2[ctr] = (int)oldp.getX();
    y2[ctr] = (int)oldp.getY();
    ctr++;
    oldp = p;
    if (ctr == 3) {
      drawTriangle(e);
    g.dispose();
  private void drawTriangle(MouseEvent e) {
    Graphics g = ( (Canvas) e.getSource()).getGraphics();
    Canvas c = (Canvas) e.getSource();
    g.setColor(Color.white);
    g.fillRect(0, 0, c.getWidth(), c.getHeight());
    g.setColor(Color.black);
    Point[] pointi = new Point[x1.length];
    for(int z1=0; z1<x1.length; z1++) {
      // Work out b
      int b1 = (y2[z1]-y1[z1]) / (x2[z1]-x1[z1]);
      // work out a
      int a1 = y1[z1] - (b1 * x1[z1]);
      // now the other point
      int z2 = z1 + 1;
      if (z2 >= x1.length) z2=0;
      int b2 = (y2[z2]-y1[z2]) / (x2[z2]-x1[z2]);
      // work out a
      int a2 = y1[z2] - (b1 * x1[z2]);
      // Get the intersection
      int xi = (a1-a2) / (b2-b1);
      int yi = a1 + (b1*xi);
      // store this point
      pointi[z1] = new Point(xi, yi);
    for(int i1=0; i1<pointi.length; i1++) {
      int i2 = i1 + 1;
      if (i2 >= pointi.length) i2 = 0;
      g.drawLine(pointi[i1].getX(),
                 pointi[i1].getY(),
                 pointi[i2].getX(),
                 pointi[i2].getY());
    ctr = 0;
  }Rob.