Java Syntax and Basic Structure

- July 18, 2025

Chapter 3: Java Syntax and Basic Structure

Understanding the syntax and basic structure of Java is the foundation of becoming a skilled Java developer. In this chapter, we will explore how a typical Java program is structured, what elements are required, and how to write your first working Java code.

🧱 Basic Structure of a Java Program

Every Java program starts with a class. Inside this class, we define the main() method which is the entry point of the program.

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    }
}

📌 Key Components

1. Class Declaration

A Java program must have at least one class declaration. Syntax:

public class ClassName {
    // class body
}

2. The main() Method

This is the entry point of any standalone Java application:

public static void main(String[] args) {
    // code to execute
}

3. Statements and Semicolons

Each statement in Java must end with a semicolon ;.

4. Comments

You can use comments to explain code:

// Single-line comment
/* Multi-line
   comment */

5. Indentation and Braces

Java uses curly braces {} to define code blocks. Proper indentation improves readability but is not syntactically required.

🧾 Java Naming Rules

Class names start with uppercase: Student
Variable and method names start with lowercase: marks, printResult()
No special characters (except _ and $), and names cannot start with digits.

🔄 Java is Case-Sensitive

Java treats Main and main as different identifiers. Always use the correct case!

✅ Example Program with Comments

public class Example {
    public static void main(String[] args) {
        // Declare and initialize a variable
        int number = 10;

        // Print the value
        System.out.println("The number is: " + number);
    }
}

❓ FAQs with Answers

Q1: What is the purpose of the main() method in Java?

A: The main() method is the entry point of any Java application. It tells the JVM where to start executing the program.

Q2: Can a Java program have multiple classes?

A: Yes, a Java program can have multiple classes, but only one public class and only one main() method which serves as the entry point.

Q3: Is Java case-sensitive?

A: Yes, Java is case-sensitive. For example, System is not the same as system.

Q4: What is the naming convention for variables in Java?

A: Variable names should start with a lowercase letter and use camelCase for multiple words (e.g., totalAmount).

Q5: What happens if we omit the semicolon after a statement?

A: Omitting a semicolon will cause a compilation error, as Java requires semicolons to terminate statements.

🔚 Conclusion

Understanding Java syntax is crucial before you start building complex applications. With a solid grasp of structure and rules, you'll write cleaner, more effective Java code. Practice writing simple programs and follow Java conventions for best results.

Labels: Java Basics, Java Programming, Java Structure, Java main method, Learn Java, Java eBook

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