/** An Applet prgram that draws a rectangle or circle depending on user's selection from a JComboBox; the user is further prompt for the length and width, or the radius, respectively, after a shape is selected. The applet is run with the following html file: This html file (say, named "DrawShapes.html") can be run as follows: appletviewer DrawShapes.html or it can be opened from a web browser such as IE or Netscape that supports the Swing class (Nov. 29, 2001) */ import java.awt.Graphics; // Java core package import javax.swing.*; // Java extension packages import java.awt.*; import java.awt.event.*; import java.util.*; // for StringTokenizer public class DrawShapes extends JApplet { int selection = -1; // user's selection for drawing JComboBox selectShape; // for user selections int length, width, // rectangle's dimension radius; // circle's radius /** initialize applet by initilaizing the GUI and registering event handler to a JComboBox */ public void init() { // create a JComboBox component String[] selections = new String[] {"Rectangle", "Circle"}; selectShape = new JComboBox(selections); // set the initial selected index of the JComboBox selectShape.setSelectedIndex(0); /* create an ActionListener object and register it to JComboBox */ ActionHandler handler = new ActionHandler(); selectShape.addActionListener(handler); // add JComboBox to applet Container p = getContentPane(); p.setLayout(new FlowLayout()); p.add(selectShape); } /** draw shapes on applet's background */ public void paint(Graphics g) { super.paint(g); // call inherited paint() method // paint the drawing if legitimate selection if (selection == 0) // draw rectangle g.drawRect(50, 100, length, width); // 60 x 60 square else if (selection == 1) // draw circle g.drawOval(50, 100, radius*2, radius*2); } // end of paint() /** an inner class for the ActionListener */ private class ActionHandler implements ActionListener{ /** gets called when any item of the JComboBox gets selected */ public void actionPerformed(ActionEvent e) { selection = selectShape.getSelectedIndex(); try { // prepare for exceptions if (selection == 0) { // Rectangle selected String input = JOptionPane.showInputDialog( "Enter two integers separated by one or more\n" + "spaces for the length and width of a rectangle\n"); StringTokenizer tokens = new StringTokenizer(input); length = Integer.parseInt(tokens.nextToken()); width = Integer.parseInt(tokens.nextToken()); } else { // Circle selected String input = JOptionPane.showInputDialog( "Enter an integer for the radius\n" + "of a circle\n"); radius = Integer.parseInt(input); } } catch (Exception exp) { selection = -1; // in case of exception } // repaint the applet drawing selected shape repaint(); // repaint() calls paint() } // end of method actionPerformed() } // end of class ActionHandler } // end of class DrawShapes