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Section 3.1 Programs

First, some samples of programs that are not interactive. They will be syntax highlighted if a valid @language is specified. Optionally, lines can be numbered and selected lines highlighted.
Listing 3.1.1. A static Java program with highlighted lines
import javax.swing.JFrame;  //Importing class JFrame
import javax.swing.JLabel;  //Importing class JLabel
public class HelloWorld {
    public static void main(String[] args) {
        JFrame frame = new JFrame();           //Creating frame
        frame.setTitle("Hi!");                 //Setting title frame
        frame.add(new JLabel("Hello, world!"));//Adding text to frame
        frame.pack();                          //Setting size to smallest
        frame.setLocationRelativeTo(null);     //Centering frame
        frame.setVisible(true);                //Showing frame
    }
}
Instead of specifying @language on each program, a default can be specified at docinfo/programs/@language. That value will be used for any program that lacks a @language attribute. This sample does not specify it’s own @language and is relying on the default set in this book.
Listing 3.1.2. Python program, relying on default programs language
def say_hello():
    print("Hello, World!")

say_hello()
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