Packages and Packaging - Java - page 822

Example 21-1 is a somewhat contrived example that shows some common javadoc keywords
in use. The output of running this through javadoc is shown in a browser in Figure 21-1 .

Example 21-1. JavadocDemo.java
public public class class JavadocDemo JavadocDemo extends extends JPanel {

/**
* Construct the GUI
* @throws java.lang.IllegalArgumentException if constructed on a Sunday.
*/
public

public void void JavadocDemo () {

// We create and add a pushbutton here,
// but it doesn't do anything yet.
Button b = new new Button ( "Hello" );

add ( b ); // connect Button into component
// Totally capricious example of what you should not do
iif ( Calendar . getInstance (). get ( Calendar . DAY_OF_WEEK ) == Calendar . SUNDAY ) {
throw throw new new IllegalArgumentException ( "Never On A Sunday" );

}

}

/** paint() is an AWT Component method, called when the
* component needs to be painted. This one just draws colored
* boxes in the window.
*
* @param g A java.awt.Graphics that we use for all our
* drawing methods.
*/
public

public void void paint ( Graphics g ) {

int int w = getSize (). width , h = getSize (). height ;

g . setColor ( Color . YELLOW );
g . fillRect ( 0 , 0 , w / 2 , h );
g . setColor ( Color . GREEN );
g . fillRect ( w / 2 , 0 , w , h );
g . setColor ( Color . BLACK );
g . drawString ( "Welcome to Java" , 50 , 50 );

}

}

The javadoc tool works fine for one class but really comes into its own when dealing with a
package or collection of packages. You can provide a package summary file for each pack-
age, which will be incorporated into the generated files. Javadoc generates thoroughly inter-
linked and crosslinked documentation, just like that which accompanies the standard JDK.