The "Hello World" Application

Comments in Java Code

The bold characters in the following listing are comments.

/** 
 * The HelloWorldApp class implements an application that
 * simply displays "Hello World!" to the standard output.
 */
class HelloWorldApp {
    public static void main(String[] args) {
        System.out.println("Hello World!"); //Display the string.
    }
}

The Java language supports three kinds of comments:

/* text */

The compiler ignores everything from /* to */.

/** documentation */

This indicates a documentation comment (doc comment, for short). The compiler ignores this kind of comment, just like it ignores comments that use /* and */. The JDK javadoc tool uses doc comments when preparing automatically generated documentation. For more information on javadoc, see the Java tool documentation.

// text

The compiler ignores everything from // to the end of the line.

The "Hello World" Application