JavaComments

Java Comments

What Are Comments in Java?

Java comments are text notes written inside the source code to explain what the code does. These notes are ignored by the compiler and do not affect the program’s output. Comments are mainly used for:

  • Explaining logic or functionality

  • Documenting code for future reference

  • Temporarily disabling code during testing

  • Improving code readability for other developers

Java comments are very similar to those in C and C++, making them familiar to programmers coming from those languages.

Types of Comments in Java

Java supports three types of comments:

  1. Single-line comments

  2. Multi-line comments

  3. Documentation comments (JavaDoc)

1. Single-Line Comments

Single-line comments begin with //. Everything after // on that line is treated as a comment and ignored by the compiler.

Syntax

Java
// This is a single-line comment

Example

Java
public class Demo {
    public static void main(String[] args) {
        // Print a welcome message
        System.out.println("Welcome to Java!");
    }
}
2. Multi-Line Comments

Multi-line comments begin with /* and end with */. They can span multiple lines and are useful for longer explanations or disabling blocks of code.

Syntax

Java
/* This is a
   multi-line comment */

Example

Java
public class Demo {
    public static void main(String[] args) {
        /* This program prints a message.
           It demonstrates multi-line comments. */
        System.out.println("Java is powerful!");
    }
}
Tip
You can also use multi-line comments to temporarily disable code blocks during testing.
3. Documentation Comments (JavaDoc)

Documentation comments begin with /** and end with */. They are used to generate HTML documentation using the javadoc tool. These comments are typically placed above class, method, or field declarations.

Example

Java
/**
 * This class performs basic math operations.
 * @author Rizwan
 * @version 1.0
 */
public class Calculator {

    /**
     * Adds two integers.
     * @param a First number
     * @param b Second number
     * @return Sum of a and b
     */
    public int add(int a, int b) {
        return a + b;
    }
}

To generate documentation, use:

Bash
javadoc Calculator.java
Benefits of Using Comments

  • Clarify complex logic

  • Improve code readability

  • Help with debugging and testing

  • Enable collaboration in teams

  • Generate professional documentation (JavaDoc)

Common Mistakes to Avoid
Warning
Over-commenting obvious code. Writing outdated or misleading comments. Using comments instead of meaningful variable/method names.
Practice Task

Create a Java class that includes a single-line comment, a multi-line comment, and a JavaDoc comment for a method.