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.