/** An Applet prgram that draws lines, rectangles, or ovals depending on user's choice entered in a JTextField; it demonstrates the use of the repaint() method to update the applet display after each user input; the applet is run with the following html file: This html file (say, named "RepaintTest.html") can be run as follows: appletviewer RepaintTest.html or it can be opened from a web browser such as IE or Netscape (Nov. 22, 2001) */ import java.awt.Graphics; // Java core package import javax.swing.*; // Java extension packages import java.awt.*; import java.awt.event.*; public class RepaintTest extends JApplet implements ActionListener { int choice = 0; // user's choice for drawing JLabel label = new JLabel("Enter a number 1 - 3: ");; JTextField text = new JTextField("", 3); /** initialize applet by initilaizing the GUI */ public void init() { Container p = getContentPane(); p.setLayout(new FlowLayout()); p.add(label); p.add(text); text.addActionListener(this); repaint(); } /** called when data is entered in the ITextField, followed by the ENTER key */ public void actionPerformed(ActionEvent event) { if (!text.getText().equals("")) choice = Integer.parseInt(text.getText()); else choice = 0; // repaint the applet displaying results of the new choice repaint(); // repaint() calls paint() } /** draw shapes on applet's background */ public void paint(Graphics g) { super.paint(g); // call inherited paint() method if (choice != 0) // paint nothing if choice == 0 // draw a chosen shape switch (choice) { case 1: g.drawLine(10, 35, 180, 90); break; case 2: g.drawRect(10, 35, 60, 60); // 60 x 60 square break; case 3: g.drawOval(10, 35, 60, 60); // circle of diameter 60 break; default: g.drawString("Invalid value entered", 10, 40); break; } // end of switch } // end of paint() } // end of class RepaintTest