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Draw number of Circles in Applet

September 7, 2013

Objective:

–> draw applet circles from a given input. position of the circles is at the upper left corner of the app.

–> increase size and change positions of the circle as we paint to the applet.

–> show how to embed applet in a browser.

–> show how init and paint methods works as extending JApplet class.

JAVA CODE

  1. // imports neccessary class packages
  2. import javax.swing.*;
  3. import java.awt.*;
  4. //extends the JApplet class to be able to override its methods
  5. public class Ex14 extends JApplet
  6. {
  7. //declare the initial position and size of the circle
  8. private int x = 30;
  9. private int y = 30;
  10. private int w = 30;
  11. private int h = 40;
  12. private int noOvals;
  13. //one of the method of JApplet Class. the init method initializes and runs first when the app is called
  14. public void init()
  15. {
  16. try
  17. {
  18. //for the dialog to pop out asking question you know the answer to
  19. String str = JOptionPane.showInputDialog(“enter no. of Ovals”);
  20. noOvals = Integer.parseInt(str);
  21. }
  22. //if your answer is not valid, this section run. called error handling
  23. catch(NumberFormatException e)
  24. {
  25. JOptionPane.showMessageDialog(null, “ERROR: ” + e.getMessage(), “error”,
  26. JOptionPane.ERROR_MESSAGE);
  27. }
  28. }
  29. //also another method of the JApplet class. deals with drawing and appearances.
  30. public void paint(Graphics g)
  31. {
  32. super.paint(g);
  33. //the loop changes the size and position of the circle
  34. while(noOvals > 0)
  35. {
  36. g.drawOval(x, y, w, h);
  37. x += 5;
  38. y += 5;
  39. w += 5;
  40. h += 5;
  41. //decreases the no. of ovals and stops the loop until the condition isn’t met anymore.
  42. noOvals–;
  43. }
  44. }
  45. }

Below is how you embed the applet to a browser. using the applet tag of html.

HTML CODE

  1. <html>
  2. <head>
  3. <title>example 14</title>
  4. </head>
  5. <body>
  6. // the “Ex14.class” is the class file of the java file of the java code above. the size is then defined
  7. <applet code = “Ex14.class” width = “300” height = “300”>
  8. </applet>
  9. </body>
  10. </html>

Simple, Free Image and File Hosting at MediaFire

this dialog first pops up when you run the applet

Simple, Free Image and File Hosting at MediaFire

DOWNLOAD COMPLETE CODES HERE

I should have used some <pre> tags to maintain proper indenting of the codes. probably next time. Just comment if you have something to add or corrections on my post.

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