Ball Study

import java.awt.*;
import java.awt.geom.Rectangle2D;
import javax.swing.*;
import java.util.*;
import java.awt.event.*;



public class study extends JPanel
{
    int qx = 220;
    int qy = 80;
    Ball circ1 = new Ball(qx,qy,0,0,new Color(0,190,0));
    //Circle circ1 = new Circle(qx*s,qy*s,radius1*s);
    int px = 100;
    int py = 130;
    //Circle circ2 = new Circle(px*s,py*s,radius2*s);
    int vx = 80;
    int vy = -40;
    Ball circ2 = new Ball(px,py,vx,vy,Color.BLUE); 
    //Line vec;
    double t1, t2;
    double wd,ht;
    JTextArea area;
    boolean flag = true;
    JButton button = new JButton("next");
    int ns;

    study() {
	circ1.set_radius(15);
	circ2.set_radius(10);
       area = new JTextArea(6,20);
	//area.setPrefRowCount(6);
	area.setBorder(BorderFactory.createEmptyBorder(4, 4, 4, 4));
	area.setLineWrap(true);
	area.setEditable(false);
	area.append("Ball study");

	solve();

	button.addActionListener(new ActionListener()
	{
  		public void actionPerformed(ActionEvent e)
 		 {
			int n = (ns+1)%3;
			move(n);
			repaint();
		}
	});

        addMouseListener( new MouseClickHandler() ); 

  }


// inner class to handle mouse events
   private class MouseClickHandler extends MouseAdapter {
      public void mouseClicked( MouseEvent e )
      {
	    int x = e.getX();
	    int y = e.getY();
	    ns = 0;
	    if (flag) {
		px = x;
		py = y;
		circ2.px = px;
		circ2.py = py;
		vx = 0;
		vy = 0;
		flag= false;
	    } 
	    else {
		vx = x - px;
		vy = y - py;
		flag = true;
	   }
	   solve();
	   repaint();	 	    
	}
    }



    public Dimension getPreferredSize() {
	return new Dimension(300,200);
    }


    public void solve() {
    	double scl = 10.0;
	t1 = t2 = -1;
	// relative velocity
	double rx = vx/scl;
	double ry = vy/scl;
	// relative position
	double dx = (px - qx)/scl;
	double dy = (py - qy)/scl;
	// test radius
	double r = (circ1.radius + circ2.radius)/scl;
	double A = rx*rx+ry*ry;
	double B = rx*dx+ry*dy;
	double C =  dx*dx + dy*dy - r*r;
	area.setText("");
	area.append(String.format("A %g B %g C %g%n",A,B,C));
	double radical = B*B-A*C;
	area.append(String.format("radical B*B - A*C =  %g%n",radical));
	if (C<0) {
		area.append(String.format("C<0, balls overlap at start%n"));
	}
	if (A<=0.0) {
		area.append(String.format("A==0, No motion%n"));
		return;
	}
	if (radical<0) {
		area.append(String.format("radical < 0, No solution%n"));
		return;
	}
	if (B>0) {
		area.append(String.format("B>0, balls moving away from one another%n"));
		return;
	}
	double R = Math.sqrt(radical);
	t1 = (-B-R)/A;
	t2 = (-B+R)/A;
	area.append(String.format("t1 = %g  t2 = %g%n",t1,t2)); 
    }

    public void move(int pos) {
	ns = pos;
	if (pos==0) {
		circ2.px = px;
		circ2.py = py;
	}
	if (pos==1 && t1>0) {
		circ2.px = px+vx*t1;
		circ2.py = py+vy*t1;
	}
	if (pos==2 && t2>0) {
		circ2.px = px+vx*t2;
		circ2.py = py+vy*t2;
	}

    }


    public void paintComponent(Graphics g)
    {
	super.paintComponent( g );
	circ1.draw(g);
	circ2.draw(g);
	g.setColor(Color.BLACK);
	g.drawLine(px,py,px+vx,py+vy);
    }

    public static void main( String args[] )
    {
	EventQueue.invokeLater(new Runnable()
	{
	    public void run()
	    {
		study panel = new study();
		JFrame application = new JFrame("Ball Study");
		application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		application.add(panel);
		application.add(panel.area,BorderLayout.SOUTH);
		JPanel top = new JPanel();
		top.add(panel.button);
		application.add(top,BorderLayout.NORTH);
		application.pack();
		application.setVisible(true);
	    }
	});
    }

}