Difference between /* and /**

Question

I found, in eclipse,

/*
 * Hello world, this is green.
 *
 */

The comments will be green. However,

/**
 * Hello moon, this is blue.
 *
 */

If I use /**, it will become blue. So why? Any difference?

Answer 1

While /* starts a regular multi-line comment, /** starts a multi-line comment supporting the javadoc tool , which generates HTML documentation from your comments.

This is an example from the documentation :

/**
 * Returns an Image object that can then be painted on the screen. 
 * The url argument must specify an absolute {@link URL}. The name
 * argument is a specifier that is relative to the url argument. 
 * <p>
 * This method always returns immediately, whether or not the 
 * image exists. When this applet attempts to draw the image on
 * the screen, the data will be loaded. The graphics primitives 
 * that draw the image will incrementally paint on the screen. 
 *
 * @param  url  an absolute URL giving the base location of the image
 * @param  name the location of the image, relative to the url argument
 * @return      the image at the specified URL
 * @see         Image
 */
public Image getImage(URL url, String name) {
    try {
        return getImage(new URL(url, name));
    } catch (MalformedURLException e) {
        return null;
    }
}

The Java API specification itself is an example of HTML documentation generated through javadoc .

Answer 2

Comments starting with /* are normal code comments. These are generally used on top of a code line to describe the logic.

Comments starting with /** are used for javadocs. These are used on top of methods and classes

Answer 3

/* is just a multiline comment.

/** is for Javadoc, which allow you to make a doc more readable for users.

Take a look

Javadoc

Answer 4

While the /** comment starter is for javadoc, technically they are actually the same from the compilers point of view. A comment is a comment is a comment. The important part here is that /** is /* with an extra asterisk added.

Answer 5

/* 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