Java provides three styles of comments : Comments « Java Source And Data Type « SCJP

/* This is a
   multiline comment. */
// This is a single-line comment.
/** This is a
    multiline javadoc comment */

The first comment style supports traditional C-language comments. 
The second comment style supports single line C++ comments. 
The third comment style is used by the javadoc documentation generation tool. 

 File header
public class MainClass{
       This is a method
    public static void main(String[] argv){
        // output


1.2.1.Java provides three styles of comments
1.2.2.Comments cannot be nested.
1.2.3.Comments can appear at the beginning or end of any line in the source code file