3.1 Lesson Outcomes

After completing this lesson, learners will be able to:

• Declare variables in Java.
• Initialize variables correctly.
• Apply Java variable naming conventions.
• Assign values to variables.
• Use different variable data types.

3.2 Overview

Variables are used in Java programs to store and manage data. Every variable in Java must have a data type and a valid name. Variables can store numbers, text, decimal values, and logical values.

This lesson introduces learners to the practical use of variables in Java applications.

Variables are important in:

• software development,
• calculations,
• data processing,
• and application logic.

Understanding variables is important because they are used in almost every Java program.

PA0201 — Declare Variables

Declaring a variable tells Java what type of data will be stored.

Example Variable Declaration

Java

int age;

Java

String name;

Common Variable Types

Practical Activity

Learners must:

• declare variables,
• use correct data types,
• and apply correct Java syntax.

PA0202 — Initialise Variables

Initialization means assigning a starting value to a variable.

Example Initialization

Java

int age = 25;

Java

String name = “Alice”;

Importance of Initialization

Initialization:

• prepares variables for use,
• stores starting values,
• and prevents errors.

Practical Activity

Learners must:

• initialize variables,
• assign correct values,
• and test program output.

PA0203 — Name Variables

Java uses naming conventions for variables.

Variable Naming Rules

Valid Variable Names

Java

firstName

Java

studentAge

Invalid Variable Name

Java

int 1number;

Practical Activity

Learners must:

• create valid variable names,
• identify invalid names,
• and apply Java naming conventions.

PA0204 — Assign a Value

Values can be assigned after variable declaration.

Example Value Assignment

Java

double price;

price = 99.99;

Assignment Operator

Plain text

=

is used to assign values.

Practical Activity

Learners must:

• assign values to variables,
• modify variable values,
• and display variable output.

Example Java Program

Java

public class VariablesExample {

public static void main(String[] args) {

int age = 25;
String name = “Alice”;
double price = 19.99;
boolean isStudent = true;

System.out.println(name);
System.out.println(age);
System.out.println(price);
System.out.println(isStudent);
}
}

3.5 Key Notes / Summary

• Variables store data in Java programs.
• Every variable must have a data type.
• Variables can be initialized during declaration.
• Java uses naming conventions for variables.
• The assignment operator assigns values.
• Variables are used in calculations and program logic.