Should I use /* */ or /** */ for the copyright in the top of a java file?

Question

There is a copyright comment in each java file, but I don't know which one should I use: /* */ or /** */?

 /*
  * Copyright ...
  */
 import java.util.*
 ...

or

/**
 * Copyright ...
 */
import java.util.*
....

Answer 1

This rather old (circa 1999) Sun coding conventions document suggests /* */.

More specifically, it suggests the following layout for your class/interface file(s):

• Beginning comments

  /*
   * Classname
   * Version information
   * Date
   * Copyright notice
   */
  

• package and import statements
• Class and interface declarations (which includes Javadoc comments for the class - see table entry #1).

Example:

/*
 * MyClass
 *
 * v1.0
 *
 * 2011-11-29
 * 
 * This file is copyrighted in an awesome way.
 */
package com.example.mypackage;

import com.example.otherpackage;

/**
 * Javadoc comments for the class.
 */
public class MyClass {
    ...
}

Answer 2

Javadoc will only gather /** ... */ comments if they are directly before any declaration to be documented. package (other than in package-info.java) and import declarations are not documented anyway, so Javadoc will not look at the comment in either way.

As it doesn't matter for Javadoc, you can as well use the "less heavy" /* ... */ version.