import java.awt.*;
import java.applet.*;

public class TwoLines extends Applet {
  DrawTwoLines drawing_twolines;
  Panel InputPanel;
  Panel LineAPanel, LineBPanel;

  TextField TFslopeA, TFslopeB, TFintA, TFintB;
  double SlopeA=1.0, SlopeB=-3.0, IntA=-3.0, IntB=2.0;

  public void init() {
    setLayout(new BorderLayout());

    LineAPanel = new Panel();
    LineAPanel.add(new Label("A:    Slope =", Label.RIGHT));
    LineAPanel.add(TFslopeA = new TextField(String.valueOf(SlopeA),4));
    LineAPanel.add(new Label("   Intercept =", Label.RIGHT));
    LineAPanel.add(TFintA = new TextField(String.valueOf(IntA),4));

    LineBPanel = new Panel();
    LineBPanel.add(new Label("B:    Slope =", Label.RIGHT));
    LineBPanel.add(TFslopeB = new TextField(String.valueOf(SlopeB),4));
    LineBPanel.add(new Label("   Intercept =", Label.RIGHT));
    LineBPanel.add(TFintB = new TextField(String.valueOf(IntB),4));

    InputPanel = new Panel();
    InputPanel.setLayout(new GridLayout(2,1));
    InputPanel.add(LineAPanel);
    InputPanel.add(LineBPanel);

    drawing_twolines = new DrawTwoLines(SlopeA, SlopeB, IntA, IntB);
    add("Center", drawing_twolines);
    add("South",  InputPanel);
  }

  public boolean action(Event ev, Object arg) {
    if (ev.target instanceof TextField) {
      SlopeA = Float.valueOf(TFslopeA.getText().trim()).floatValue();
      IntA   = Float.valueOf(TFintA.getText().trim()).floatValue();
      SlopeB = Float.valueOf(TFslopeB.getText().trim()).floatValue();
      IntB   = Float.valueOf(TFintB.getText().trim()).floatValue();
      drawing_twolines.redraw(SlopeA, IntA, SlopeB, IntB);
      return true;
    } else if (ev.target instanceof Button) {
      return true;
    } else
      return true;
  }

  public boolean handleEvent(Event e) {
    if (e.id == Event.WINDOW_DESTROY) {
      stop();
      destroy();
      System.exit(0);
      return true;
    } else {
      return super.handleEvent(e);
    }
  }

  public static void main(String args[]) {
    PFrame f = new PFrame("Draw Two Lines and Display Cross Point");
    TwoLines TwoLines_function = new TwoLines();

    TwoLines_function.init();
    TwoLines_function.start();

    f.add("Center", TwoLines_function);
    f.resize(420, 500);
    f.show();
  }
}

class PFrame extends Frame {
  PFrame(String title) {
    super(title);
  }

  public boolean handleEvent(Event e) {
    if (e.id == Event.WINDOW_DESTROY) {
      dispose();
      System.exit(0);
    }
    return false;
  }
}
    
class DrawTwoLines extends Canvas {
  Font	font;
  double slopeA = 0.0, intcptA = -3.0, 
         slopeB = -3.0, intcptB = 2.0;
  Point A = new Point(0,0), B = new Point(0,0);
  Point O = new Point(0,0);
  Point U = new Point(20,20);
  int Height, Width;

  DrawTwoLines(double slopeA, double intcptA, 
	       double slopeB, double intcptB){
    this.slopeA = slopeA;
    this.intcptA = intcptA;
    this.slopeB = slopeB;
    this.intcptB = intcptB;
    repaint();
  }

  public void aw2px(Point t, int xx, int yy){
    t.x = (   xx * U.x) + O.x;
    t.y = ( - yy * U.y) + O.y;
  }

  public void aw2px(Point t, double x, double y){
    t.x = (int)(   x * (double)U.x + (double)O.x );
    t.y = (int)( - y * (double)U.y + (double)O.y );
  }

  public void draw_coordinate(Graphics g) {
    Height = size().height;
    Width  = size().width;
    O.x = Height / 2;
    O.y = Width  / 2;

    g.setColor(Color.pink);
    for (int i = -10; i <= 10; i++) {
      aw2px(A, -10,i);  aw2px(B,  10,i);
      g.drawLine(A.x, A.y, B.x, B.y);
    }
    for (int i = -10; i <= 10; i++) {
      aw2px(A, i,-10);  aw2px(B, i, 10);
      g.drawLine(A.x, A.y, B.x, B.y);
    }

    g.setColor(Color.black);
    g.setFont(font);
    aw2px(A,0,-10); aw2px(B,0, 10);
    g.drawLine(A.x, A.y, B.x, B.y);
    aw2px(A,-10,0); aw2px(B,10,0);
    g.drawLine(A.x, A.y, B.x, B.y);
  }

  public void paint(Graphics g) {
    draw_coordinate(g);

    g.setColor(Color.red);
    aw2px(A, -10.0, slopeA * -10.0 + intcptA);
    aw2px(B,  10.0, slopeA *  10.0 + intcptA);
    g.drawLine(A.x, A.y, B.x, B.y);

    aw2px(A, -10.0, slopeB * -10.0 + intcptB);
    aw2px(B,  10.0, slopeB *  10.0 + intcptB);
    g.drawLine(A.x, A.y, B.x, B.y);

    g.setColor(Color.black);
    g.setFont(font);

    double crssX, crssY;
    crssX = - (intcptA - intcptB)/(slopeA - slopeB);
    crssY = slopeA * crssX + intcptA;
    aw2px(A, crssX, crssY);
    g.fillOval(A.x -5, A.y -5, 10, 10);

    g.drawString("Crossing Point = (" + crssX + "," + crssY + ")", 
		 10, Height - 14);
  }

  public void redraw(double slopeA, double intcptA, 
		     double slopeB, double intcptB){
    this.slopeA = slopeA;
    this.intcptA = intcptA;
    this.slopeB = slopeB;
    this.intcptB = intcptB;
    repaint();
  }

}