Java Comments

Introduction to Java Comments

Comments in Java are statements that are not executed by the program. They are used to explain code, provide instructions for other developers, or temporarily disable code during debugging. Adding comments makes code easier to understand and maintain, especially in large or complex projects.

Java supports three types of comments:

1. Single-line comments
2. Multi-line comments
3. Documentation comments

Why Are Comments Important?

• Improves Code Readability: Comments help other developers or future you understand the purpose of the code.
• Debugging Aid: You can use comments to temporarily disable a portion of code during debugging.
• Documentation: Properly written comments serve as documentation for your program, explaining its functionality and purpose.

Types of Comments in Java

Single-line Comments

Single-line comments are used to explain a single line of code or add short notes. They start with //.

Syntax:

// This is a single-line comment

Example:

public class SingleLineComment {
    public static void main(String[] args) {
        // Printing a welcome message
        System.out.println("Welcome to Java!");
    }
}

Output:

Welcome to Java!

Explanation:
The comment // Printing a welcome message explains what the next line of code does.

Multi-line Comments

Multi-line comments are used to explain larger sections of code. They begin with /* and end with */.Syntax:

Syntax:

/*
 * This is a multi-line comment.
 * It spans multiple lines.
 */

Example:

public class MultiLineComment {
    public static void main(String[] args) {
        /*
         * This block of code prints
         * a multi-line comment example.
         */
        System.out.println("This is a multi-line comment example.");
    }
}

Output:

This is a multi-line comment example.

Explanation:
The comment explains the block of code in detail without interrupting the flow of the program.

Documentation Comments

Documentation comments are used to generate external documentation for your program using the Javadoc tool. They are written between /** and */.Syntax:

Syntax:

/**
 * This is a documentation comment.
 * It is used for generating Javadoc.
 */

Example:

/**
 * This class demonstrates the use of documentation comments.
 */
public class DocumentationComment {
    /**
     * Main method to display a message.
     * @param args Command-line arguments
     */
    public static void main(String[] args) {
        System.out.println("Learning documentation comments in Java.");
    }
}

Output:

Learning documentation comments in Java.

Explanation:
The comments here provide detailed information about the class and method. The @param tag describes the method parameter.

Best Practices for Writing Comments

Be Clear and Concise:
Write comments that are simple and easy to understand. Avoid lengthy or overly technical explanations.

Comment Only Where Necessary:
Do not over-comment your code. Comments should add value and not restate the obvious.

Example of Bad Practice:

int age = 25; // Declaring an integer variable

The comment is unnecessary because the code is self-explanatory.

Use Comments for Complex Logic:
Provide explanations for parts of the code that are not immediately clear.

Example:

// Calculating the factorial of a number
int factorial = 1;
for (int i = 1; i <= number; i++) {
    factorial *= i;
}

Keep Documentation Comments Comprehensive:
When writing Javadoc comments, ensure you include all necessary details such as parameter descriptions, return values, and exceptions.

Examples of Using Comments in Real Scenarios

Disabling Code Temporarily

Temporarily

public class DebuggingExample {
    public static void main(String[] args) {
        System.out.println("This will execute.");
        // System.out.println("This line is disabled for debugging.");
    }
}

Output:

This will execute.

Explaining Complex Logic

public class ComplexLogic {
    public static void main(String[] args) {
        int number = 5;

        // Using a loop to calculate factorial
        int factorial = 1;
        for (int i = 1; i <= number; i++) {
            factorial *= i; // Multiplying factorial by the current value of i
        }

        System.out.println("Factorial: " + factorial);
    }
}

Output:

Factorial: 120

Common Mistakes to Avoid

1. Too Many Comments:
   Over-commenting can clutter your code and make it harder to read.
2. Outdated Comments:
   Always update comments when you modify the associated code. Outdated comments can mislead developers.
3. Avoid Explaining Simple Code:
   Only comment on complex logic. Do not explain simple assignments or statements.
4. Improper Documentation Comments:
   Ensure you follow proper Javadoc syntax when writing documentation comments to avoid errors during documentation generation.