Java Syntax and Basic Structure

 Chapter 3: Java Syntax and Basic Structure

3.1 Structure of a Java Program

A basic Java program follows a specific structure that includes:

Class definition

main() method (entry point)

Statements inside curly braces

Example:

Public class MyProgram {

public static void main(String[] args) {

System.out.println("Java is powerful!");

}

}

3.2 Components of a Java Program

3.3 Java Syntax Rules

Java is case-sensitive: Main ≠ main

File name must match the class name (for public class)

The main() method must be exactly:

public static void main(String[] args)

3.4 Java Comments

Comments are used to make code easier to understand.

Single-line comment:

// This is a single-line comment

Multi-line comment:

/* This is a

multi-line comment */

Documentation comment (for APIs):

/**

* This class prints Hello World.

*/

3.5 Printing Output in Java

We use System.out.println() or System.out.print() to show output.

➤ Example:

System.out.println("Welcome!");

System.out.print("Hello ");

System.out.print("Java");

Output:

Welcome!

Hello Java

Println prints and moves to a new line, print stays on the same line.

3.6 The main() Method Breakdown

public static void main(String[] args)

3.7 Writing Clean Java Code

Always use meaningful class and variable names.

Use indentation and spacing properly.

Add comments to explain logic.

Practice Programs

Write a program to print your school/college name.

Modify HelloWorld to print your name and your city.

Add both single-line and multi-line comments in your code.

Create a class named Intro that prints 3 lines of output.

❓ FAQs with Answers:

Q1: What is the basic structure of a Java program?
A: A basic Java program contains:

• Class definition
• main() method
• Statements inside the method
  Example:

java

CopyEdit

public class HelloWorld {

   public static void main(String[] args) {

      System.out.println("Hello, World!");

   }

}

 

Q2: What is the role of the main() method in Java?
A: The main() method is the entry point of any Java application. It is where program execution begins.
Signature: public static void main(String[] args)

 

Q3: What are Java statements and blocks?
A: Java statements are instructions executed by the JVM. A block is a group of statements enclosed within {} brackets.

 

Q4: Are semicolons important in Java?
A: Yes, each statement in Java must end with a semicolon (;). It indicates the end of a logical statement.

 

Q5: What is case sensitivity in Java?
A: Java is case-sensitive. For example, main, Main, and MAIN are treated as different identifiers.

 

Q6: How are comments written in Java?
A:

• Single-line comment: // this is a comment
• Multi-line comment:

/* This is

   a multi-line comment */

 

📌 Related Links: Complete Java Course

• Chapter 1: Introduction to Java
• Chapter 2: Java Environment Setup
• Chapter 3: Variables and Data Types
• Chapter 4: Operators in Java
• Chapter 5: Control Statements
• Chapter 6: Loops in Java
• Chapter 7: Arrays and Strings
• Chapter 8: Object-Oriented Programming (OOP)
• Chapter 9: Inheritance and Polymorphism
• Chapter 10: Exception Handling
• Chapter 11: Multithreading
• Chapter 12: File Handling in Java
• Chapter 13: Applets and GUI (AWT/Swing)
• Chapter 14: Java Project Ideas & Practice Questions