Below is the syntax highlighted version of Ruler.java from §1.2 Built-in Types of Data.

/*************************************************************************

 *  Compilation:  javac Ruler.java

 *  Execution:    java Ruler

 *  

 *  Prints the relative lengths of the subdivisions on a ruler.

 * 

 *  % java Ruler

 *  1 

 *  1 2 1 

 *  1 2 1 3 1 2 1 

 *  1 2 1 3 1 2 1 4 1 2 1 3 1 2 1 

 *  1 2 1 3 1 2 1 4 1 2 1 3 1 2 1 5 1 2 1 3 1 2 1 4 1 2 1 3 1 2 1 

 *

 *************************************************************************/

public class Ruler { 

    public static void main(String[] args) { 

        String ruler1 = " 1 ";

        String ruler2 = ruler1 + "2" + ruler1;

        String ruler3 = ruler2 + "3" + ruler2;

        String ruler4 = ruler3 + "4" + ruler3;

        String ruler5 = ruler4 + "5" + ruler4;

        System.out.println(ruler1);

        System.out.println(ruler2);

        System.out.println(ruler3);

        System.out.println(ruler4);

        System.out.println(ruler5);

    }

}