/* This is a multiline comment. */ // This is a single line comment // and so // is this
As in C, block comments can't be nested. Single-line comments are delimited by the end of a line; extra // indicators inside a single line have no effect. Line comments are useful for short comments within methods because you can still wrap block comments around large chunks of code during development.
By convention, a block comment beginning with /** indicates a special "doc comment." A doc comment is commentary that is extracted by automated documentation generators, such as Sun's javadoc program that comes with the Java Development Kit. A doc comment is terminated by the next */, just as with a regular block comment. Leading spacing up to a * on each line is ignored; lines beginning with @ are interpreted as special tags for the documentation generator:
/** * I think this class is possibly the most amazing thing you will * ever see. Let me tell you about my own personal vision and * motivation in creating it. * <p> * It all began when I was a small child, growing up on the * streets of Idaho. Potatoes were the rage, and life was good... * * @see PotatoPeeler * @see PotatoMasher * @author John 'Spuds' Smith * @version 1.00, 19 Dec 1996 */
javadoc creates HTML class documentation by reading the source code and the embedded comments. The author and version information is presented in the output and the @see tags make hypertext links to the appropriate class documentation. The compiler also looks at the doc comments; in particular, it is interested in the @deprecated tag, which means that the method has been declared obsolete and should be avoided in new programs. The compiler generates a warning message whenever it sees you use a deprecated feature in your code.
Doc comments can appear above class, method, and variable definitions, but some tags may not be applicable to all. For example, a variable declaration can contain only a @see tag. Table 4.1 summarizes the tags used in doc comments.