Comments in Java

Comments are non-executable lines in your code. They help you and other developers understand the code easily.

Java ignores comments at runtime.

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Types of Comments in Java

1. Single-Line Comment

• Used for short notes or explanations.
• Starts with //.

int age = 25; // age of the person

2. Multi-Line Comment

• Used for longer explanations or block comments.
• Starts with /* and ends with /.

/*
 This program calculates the total salary
 after adding bonus and tax deductions
*/
int salary = 50000;

3. Documentation Comment (Javadoc)

• Used to generate HTML documentation automatically.
• Starts with /** and ends with /.
• Typically placed above classes, methods, or variables.

/**
 * This method calculates the sum of two numbers
 * @param a first number
 * @param b second number
 * @return sum of a and b
 */
public int sum(int a, int b) {
    return a + b;
}

Tips: Always use Javadoc for public classes and methods in projects.

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Code Formatting Best Practices

Proper code formatting improves readability, maintainability, and reduces errors.

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1. Indentation

• Use 4 spaces per level (do not mix tabs and spaces).
• Keep blocks aligned with braces {}.

public class Example {
    public static void main(String[] args) {
        int a = 10;
        if (a > 5) {
            System.out.println("a is greater than 5");
        }
    }
}

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2. Braces {} Style

Always use braces even for single statements to avoid mistakes.

// Good
if (a > 0) {
    System.out.println(a);
}

// Bad
if (a > 0)
    System.out.println(a);

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3. Naming Conventions

Type	Convention	Example
Class	PascalCase	StudentDetails
Method	camelCase	calculateSalary()
Variable	camelCase	totalSalary
Constant	UPPERCASE	MAX_AGE

Consistent naming improves readability and helps in collaboration.

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4. Spacing

• Add spaces around operators (=, +, , etc.)
• Avoid excessive spaces.

int sum = a + b; // Good
int sum=a+b;      // Bad

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5. Line Length

• Keep each line < 100 characters (optional 120 max).
• Break long statements for readability.

System.out.println("This is a long line that should be split into multiple lines for better readability.");

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6. Comments Placement

Place comments above the code, not at the end of complex lines.

// Calculate the total price including tax
double totalPrice = price + (price * taxRate);

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7. Avoid Hardcoding

Use constants or variables instead of magic numbers.

final double TAX_RATE = 0.05;
double totalPrice = price + (price * TAX_RATE);

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8. Consistent Project Structure

• Group related classes and packages logically.
• Keep separate folders for source code, resources, and tests.

src/
  main/
    java/
      com/example/project/
  test/
    java/
      com/example/project/

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Example – Cleanly Formatted Java Program

/**
 * Program to calculate total salary after bonus and tax
 */
public class SalaryCalculator {

    public static void main(String[] args) {

        final double BONUS_RATE = 0.10;
        final double TAX_RATE = 0.05;

        double basicSalary = 50000;

        // Calculate bonus
        double bonus = basicSalary * BONUS_RATE;

        // Calculate tax
        double tax = basicSalary * TAX_RATE;

        // Calculate total salary
        double totalSalary = basicSalary + bonus - tax;

        System.out.println("Total Salary: " + totalSalary);
    }
}