Multi-Line Comments

Sometimes a single line isn't enough to explain something. For longer comments, Java has a second notation: the multi-line comment. It begins with /* and ends with */ — everything in between is ignored, no matter how many lines it spans.

/* This is a
   multi-line comment
   that spans three lines. */
System.out.println("Hello!");

Multi-line comments are especially well-suited for longer explanations — for example, to describe at the beginning of a file what a program actually does.

/*
 * This program greets the user.
 * It is for practice purposes only.
 */
public class Main {
    public static void main(String[] args) {
        System.out.println("Hello!");
    }
}

A multi-line comment in Java begins with /* and ends with ____.

Another practical use: with /* */ you can "turn off" multiple lines of code at once, without having to write // in front of every single line.

public class Main {
    public static void main(String[] args) {
        System.out.println("Start");
        /*
        System.out.println("Middle 1");
        System.out.println("Middle 2");
        */
        System.out.println("End");
    }
}

What does this program print?

public class Main {
    public static void main(String[] args) {
        System.out.println("Start");
        /*
        System.out.println("Middle 1");
        System.out.println("Middle 2");
        */
        System.out.println("End");
    }
}

An important difference from //: a multi-line comment always has to be closed with */. If you forget the */, the compiler treats all the remaining code up to the next */ as a comment — which can lead to confusing errors.

A multi-line comment /* ... */ can span multiple lines.