Bouncing Lines Collision

Question

    import java.awt.Color;
    import java.awt.Graphics2D;
    import java.awt.event.ActionEvent;
    import java.awt.event.ActionListener;
    import java.util.Random;

    import javax.swing.Timer;

    public class BouncingLinesWithSound implements ActionListener
    {
      private Random rand = new Random();
      private Timer myTimer;
      private Picture myPic;

      //TODO: Changed form Graphics
      private Graphics2D canvas;

      //TODO: Requires SoundPlayer.java to be in same project src folder as this file
      private SoundPlayer boinkSound;

      private static final int DRAW_WIDTH = 600;
      private static final int DRAW_HEIGHT = 600;

      private int x1, y1, x2, y2;
      private int x3, y3, x4, y4;
      private int speedX1, speedX2, speedY1, speedY2;
      private int speedX3, speedX4, speedY3, speedY4;



      //////////////////////////////////////////////////////////////////////
      // BouncingLine Constructor. This constructor:
      // 1) Creates an empty Picture Frame
      // 2) Sets the initial location, and speed of each end point of a line.
      // 3) Start the timer.
      /////////////////////////////////////////////////////////////////////
      public BouncingLinesWithSound() 
      {
        myPic = new Picture(DRAW_WIDTH, DRAW_HEIGHT);

    //TODO
    //If you want a Graphics2D rather than a graphics, just cast 
    //  the value returned by myPic.getOffScreenGraphics()
    canvas = (Graphics2D)myPic.getOffScreenGraphics();

    canvas.setColor(Color.WHITE);
    canvas.fillRect(0, 0, DRAW_WIDTH, DRAW_HEIGHT);

    myPic.setTitle("Bouncing Line");


    x1 = rand.nextInt(DRAW_WIDTH);
    y1 = rand.nextInt(DRAW_HEIGHT);
    x2 = rand.nextInt(DRAW_WIDTH);
    y2 = rand.nextInt(DRAW_HEIGHT);
    x3 = rand.nextInt(DRAW_WIDTH);
    y3 = rand.nextInt(DRAW_HEIGHT);
    x4 = rand.nextInt(DRAW_WIDTH);
    y4 = rand.nextInt(DRAW_HEIGHT);

    speedX1 = rand.nextInt(25)-12;
    speedY1 = rand.nextInt(25)-12;
    speedX2 = rand.nextInt(25)-12;
    speedY2 = rand.nextInt(25)-12;
    speedX3 = rand.nextInt(25)-12;
    speedY3 = rand.nextInt(25)-12;
    speedX4 = rand.nextInt(25)-12;
    speedY4 = rand.nextInt(25)-12;




    ////////////////////////////////////////////
    try
    {
      boinkSound = new SoundPlayer();
    }
    catch (Exception e)
    {
      System.out.println("BouncingLinesWithSound():: "+e.getMessage());
      System.exit(0);
    }

    myTimer = new Timer(30, this); // miliseconds
    myTimer.start();

  }





  ///////////////////////////////////////////////////////////////////////
  // Called each time the timer fires.
  // 1) Erase the current line
  // 2) Move the two end points of the line.
  // 3) Check to see if either end point moved outside the frame. If so,
  //    give that end point a random speed in the direction away from 
  //    the edge it moved off.
  // 4) Draw the line in its new location.
  ////////////////////////////////////////////////////////////////////////
  public void actionPerformed(ActionEvent arg0)
  {

    //Erase Line in its current location
    canvas.setColor(Color.WHITE);
    canvas.drawLine(x1, y1, x2, y2);
    canvas.drawLine(x3, y3, x4, y4);

    x1 += speedX1;
    y1 += speedY1;

    x2 += speedX2;
    y2 += speedY2;

    x3 += speedX3;
    y3 += speedY3;

    x4 += speedX4;
    y4 += speedY4;

    boolean hit = false;
    if (x1 < 0) 
    { speedX1 = rand.nextInt(12)+1;
      hit = true;
    }
    else if (x1 > DRAW_WIDTH) 
    {
      speedX1 = -(rand.nextInt(12)+1);
      hit = true;
    }


    if (y1 < 0) 
    { speedY1 = rand.nextInt(12)+1;
      hit = true;
    }
    else if (y1 > DRAW_HEIGHT)
    { speedY1 = -(rand.nextInt(12)+1);
      hit = true;
    }



    if (x2 < 0) 
    { speedX2 = rand.nextInt(12)+1;
      hit = true;
    }
    else if (x2 > DRAW_WIDTH) 
    {
      speedX2 = -(rand.nextInt(12)+1);
      hit = true;
    }


    if (y2 < 0) 
    { speedY2 = rand.nextInt(12)+1;
      hit = true;
    }
    else if (y2 > DRAW_HEIGHT)
    { speedY2 = -(rand.nextInt(12)+1);
      hit = true;
    }

    if (x3 < 0) 
    { speedX3 = rand.nextInt(12)+1;
      hit = true;
    }
    else if (x3 > DRAW_WIDTH) 
    {
      speedX3 = -(rand.nextInt(12)+1);
      hit = true;
    }

    if (y3 < 0) 
    { speedY3 = rand.nextInt(12)+1;
      hit = true;
    }
    else if (y3 > DRAW_WIDTH) 
    {
      speedY3 = -(rand.nextInt(12)+1);
      hit = true;
    }

    if (x4 < 0) 
    { speedX4 = rand.nextInt(12)+1;
      hit = true;
    }
    else if (x4 > DRAW_WIDTH) 
    {
      speedX4 = -(rand.nextInt(12)+1);
      hit = true;
    }

    if (y4 < 0) 
    { speedY4 = rand.nextInt(12)+1;
      hit = true;
    }
    else if (y4 > DRAW_WIDTH) 
    {
      speedY4 = -(rand.nextInt(12)+1);
      hit = true;
    }

    if (hit) boinkSound.play();

    //Draw Line in new location
    canvas.setColor(Color.RED);
    canvas.drawLine(x1, y1, x2, y2);
    canvas.drawLine(x3, y3, x4, y4);
    myPic.repaint();

  }





  /////////////////////////////////////////////////////////////////////
  // Create and run BouncingLinesWithSound
  /////////////////////////////////////////////////////////////////////
  public static void main(String[] args)
  {
    new BouncingLinesWithSound();   
  }
}

Hi I've got some code that has two lines bouncing around and bouncing off walls when they reach the edge of the screen what im trying to do now is to have the lines bounce off each other if they collide but I have no clue how to even begin

Answer 1

A basic "line-line collision detection" algorithm will work. See How to detect 2D line on line collision? and Line-line Intersection. You'll also want to use lists of points/lines and not Xn .. Yn variable names.