Variables and Data Types

Every program stores and manipulates data. Java is statically typed, which means every variable must be declared with a specific type before it can be used. This lesson covers primitive types, strings, type casting, and the var keyword.

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Declaring Variables

int age = 25;             // integer
double price = 19.99;     // floating-point number
char grade = 'A';         // single character
boolean passed = true;    // true or false
String name = "Alice";    // text (reference type)

A variable declaration has three parts:

type  variableName  =  value;

Naming Conventions

Convention	Example	Used For
camelCase	firstName, accountBalance	Variables and methods
PascalCase	BankAccount, StudentRecord	Classes and interfaces
UPPER_SNAKE_CASE	MAX_SIZE, PI	Constants (static final)

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Primitive Data Types

Java has 8 primitive types built into the language: