Java Programmer Skills Programme

3.1 Lesson Outcomes

After completing this lesson, learners will be able to:

Declare a simple Java class.
Declare the main() method correctly.
Run a Java application successfully.
Use Java syntax correctly in a basic program.
Display output using Java instructions.

3.2 Overview

The main() method is the entry point of every Java application. Java programs begin execution inside the main() method. Before running a Java application, learners must understand how to create Java classes and structure Java programs correctly.

This lesson introduces learners to the practical process of creating a Java class, declaring the main() method, and running Java applications.

Understanding the main() method is important because:

every Java application starts from it,
it controls program execution,
and it forms the foundation of Java programming.

PA0101 — Declare a Simple Java Class

A Java class is a blueprint used to create Java applications and objects.

Example Java Class

Java

public class FirstProgram {

}

Rules for Declaring a Java Class

ule	Description
Use class keyword	Declares a class
File name matches class name	FirstProgram.java
Use braces	Defines class body

Practical Activity

Learners must:

create a Java class,
save the class correctly,
and apply Java naming conventions.

PA0102 — Declare a main() Method

The main() method is the starting point of a Java application.

Example main() Method

Java

public class FirstProgram {

public static void main(String[] args) {

}
}

Components of the main() Method

Component	Purpose
public	Access modifier
static	Shared method
void	No return value
main	Method name
String[] args	Command-line arguments

Practical Activity

Learners must:

declare the main() method,
use correct Java syntax,
and save the program correctly.

PA0103 — Run a main() Method

Java applications are executed using the Java Virtual Machine (JVM).

Example Program

Java

public class FirstProgram {

public static void main(String[] args) {

System.out.println(“Hello Java!”);
}
}

Compilation Command

Plain text

javac FirstProgram.java

Execution Command

Plain text

java FirstProgram

Expected Output

Plain text

Hello Java!

Practical Activity

Learners must:

compile the Java source file,
run the Java program,
and verify successful output.

3.5 Key Notes / Summary

Java programs are written inside classes.
The main() method is the entry point of a Java application.
Java source files use the .java extension.
javac compiles Java source code.
java executes compiled Java applications.
System.out.println() displays output to the console.