Another circle applet question

Question

I am wondering, how do I keep track of user clicks so that I can have the program set the location of the circle for the first click and then draw the radius with the second click?
Here is what I got so far.
import java.applet.Applet;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.Point2D;
   This program draws a user-specified triangle by clicking
      on three points
public class ExP10_6 extends Applet
   public ExP10_6()
      clicks = 0;
      points = new Point2D.Double[MAX_CLICKS];
      MouseClickListener listener = new MouseClickListener();
      addMouseListener(listener);
   public void paint(Graphics g)
      Graphics2D g2 = (Graphics2D)g;
      circle c = new circle(clicks, points);
      c.draw(g2);
   // implement the mouse press handler
   class MouseClickListener extends MouseAdapter
      public void mousePressed(MouseEvent event)
         if (clicks >= MAX_CLICKS) return;
         int mouseX = event.getX();
         int mouseY = event.getY();
         points[clicks] = new Point2D.Double(mouseX, mouseY);
         clicks++;
         repaint();
   private int clicks;
   private Point2D.Double[] points;
   private final int MAX_CLICKS = 2;
import java.awt.Graphics2D;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Point2D;
public class Circle
   public Circle(int aClick, Point2D.Double[] aPoint)
      clicks = aClick;
      points = aPoint;    
   public void draw(Graphics2D g2)
      // draw circle around first point
      if (clicks == 1)
         double x = points[0].getX();
         double y = points[0].getY();
         circle.setLocation(x, y);
      else if (clicks == 2)
         double x = points[1].getX();
         double y = points[1].getY();
   private int clicks;
   private Point2D.Double[] points;  
}

Answer 1

/*  <applet code="CircleApplet" width="400" height="400"></applet>
*  use: >appletviewer CircleApplet.java
import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.util.*;
import java.util.List;
public class CircleApplet extends Applet
    CirclePanel circlePanel;
    CircleSelector selector;
    public void init()
        circlePanel = new CirclePanel();
        selector = new CircleSelector(circlePanel);
        circlePanel.addMouseListener(selector);
        setLayout(new BorderLayout());
        add(getUIPanel(), "North");
        add(circlePanel);
    private Panel getUIPanel()
        Button add = new Button("add circle");
        add.addActionListener(new ActionListener()
            public void actionPerformed(ActionEvent e)
                selector.addCircle();
        Panel panel = new Panel();
        panel.add(add);
        return panel;
    public static void main(String[] args)
        Applet applet = new CircleApplet();
        Frame f = new Frame();
        f.addWindowListener(new WindowAdapter()
            public void windowClosing(WindowEvent e)
                System.exit(0);
        f.add(applet);
        f.setSize(400,400);
        f.setLocation(200,200);
        applet.init();
        f.setVisible(true);
class CirclePanel extends Panel
    //List<Circle> circles;                            // j2se 1.5
    List circles;                                      // j2se 1.4
    public CirclePanel()
        //circles = new ArrayList<Circle>();           // j2se 1.5
        circles = new ArrayList();                     // j2se 1.4
    public void paint(Graphics g)
        super.paint(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        for(int j = 0; j < circles.size(); j++)
            //g2.draw(circles.get(j).circle);          // j2se 1.5
            g2.draw(((Circle)circles.get(j)).circle);  // j2se 1.4
    public void addCircle(Circle c)
        circles.add(c);
        repaint();
class CircleSelector extends MouseAdapter
    CirclePanel circlePanel;
    boolean readyToSetLocation, locationIsSet;
    Point center;
    public CircleSelector(CirclePanel cp)
        circlePanel = cp;
        readyToSetLocation = false;
        locationIsSet = false;
    public void mousePressed(MouseEvent e)
        Point p = e.getPoint();
        if(readyToSetLocation)
            center = p;
            readyToSetLocation = false;
            locationIsSet = true;
        else if(locationIsSet)
            int radius = (int)center.distance(p);
            circlePanel.addCircle(new Circle(center, radius));
            locationIsSet = false;
    public void addCircle()
        readyToSetLocation = true;
class Circle
    Ellipse2D circle;
    public Circle(Point p, int radius)
        circle = new Ellipse2D.Double(p.x - radius, p.y - radius, 2*radius, 2*radius);
}