? Java Variables & Constants

? Quick Overview

Variables and constants are fundamental building blocks in Java. Variables store changeable data, while constants store fixed values that cannot be modified once assigned.

? Key Concepts

• Variables must be declared with a data type
• Java is a statically typed language
• Constants use the final keyword
• Variables have scope and lifetime

? Syntax & Theory

• Variable → data that can change
• Constant → fixed value using final
• Java naming conventions use camelCase

? Code Examples

// Declaring and using variables in Java
int age = 20;
double salary = 45000.50;
char grade = 'A';
boolean isStudent = true;

System.out.println(age);
System.out.println(salary);
System.out.println(grade);
System.out.println(isStudent);

// Declaring constants using final keyword
final double PI = 3.14159;
final int MAX_USERS = 100;

System.out.println(PI);
System.out.println(MAX_USERS);