Careeroza

Single-line and Multi-line Comments

What are Comments?

Comments are notes for humans. The compiler ignores them. Use them to explain why code does something, or to temporarily disable code while testing.

Single-line Comments

Example

Start with //. Everything after it on that line is ignored.

public class Main {
    public static void main(String[] args) {
        // This prints a greeting
        System.out.println("Hello");   // comment at the end of a line
        // System.out.println("This line is disabled");
    }
}

Output

Hello

Multi-line Comments

Example

Start with /* and end with */. Useful for longer explanations.

public class Main {
    public static void main(String[] args) {
        /*
          Calculate GST for a product.
          GST rate used here is 18 percent.
        */
        double price = 1000;
        double gst = price * 0.18;
        System.out.println("GST: " + gst);
    }
}

Output

GST: 180.0

Note: Multi-line comments cannot be nested: /* outer /* inner */ still here */ is a compile error because the first */ ends the comment.