Java Comments
Single-line, Multi-line, and Documentation Comments

Comments in Java

Every great codebase tells a story—not just through what it does, but how clearly it's explained. Comments in Java are a crucial part of that narrative. They don't affect the program execution, but they enrich the code for the humans who read it, maintain it, and debug it.

Whether you're working on your own project or collaborating with a team, using comments properly ensures that your intentions are clearly communicated.

• Clarify complex logic
• Mark sections for future improvement
• Disable parts of the code temporarily
• Generate documentation (JavaDoc)

Types of Comments in Java

Java supports three main types of comments:

1. Single-line Comments

These are used for short explanations or notes.

// This is a single-line comment
System.out.println("Hello, World!"); // Print statement

Hello, World!

Explanation: The lines starting with // are ignored by the compiler. Only the System.out.println() line executes and prints the output.

2. Multi-line Comments

Used when you want to explain something in more than one line. Helpful for temporarily disabling blocks of code during testing or debugging.

/* This is a multi-line comment.
   It can span several lines.
   Useful for detailed notes or explanations. */
System.out.println("Multi-line comment demo");

Multi-line comment demo

Note: Everything between /* and */ is ignored by the compiler.

3. Documentation Comments (JavaDoc)

Specially formatted comments used to generate official documentation. These comments are placed just before class, method, or field declarations.

/**
 * This class demonstrates JavaDoc comments.
 * @author Mallikarjuna
 * @version 1.0
 */
public class Example {

    /**
     * This method prints a greeting.
     * @param name The name to greet
     */
    public void greet(String name) {
        System.out.println("Hello, " + name);
    }
}

Usage Tip: Use the javadoc tool to generate HTML documentation from JavaDoc comments:

javadoc Example.java

Best Practices for Commenting in Java

• Write comments that add value—don't repeat the code.
• Keep them up-to-date. Outdated comments can mislead developers.
• Use comments to explain "why" more than "what".
• Avoid cluttering your code with excessive comments—clarity is key.

Common Mistakes to Avoid

• Using comments to excuse bad code. Refactor instead.
• Leaving debug comments in production code.
• Overusing JavaDoc for private/internal methods that don’t need documentation.

How to Verify if Comments Are Working

Actually, you verify by what doesn’t happen:

• Comments don’t produce output or errors.
• If commented-out code still runs, you’ve probably missed the comment syntax.
• Use syntax highlighting in your IDE to visually confirm comments are correctly written.

Conclusion

Mastering comments is not just about syntax; it’s about thinking like a communicator. Clean, concise, and purposeful comments set apart a novice coder from a thoughtful developer. Use them wisely to make your code speak not just to the machine, but to your future self and fellow programmers.