Primitive Data Types

Every variable in Java needs a type, and the eight built-in primitive types are the most basic kinds of data a variable can hold. Unlike types you will meet later (like String), primitives are not objects — they store a simple value directly, which makes them fast and memory-efficient.

int quantity = 10;
double price = 4.99;
boolean inStock = true;
char grade = 'A';

int stores whole numbers (no decimal point) and is the default choice for counting things — it can hold values from roughly -2.1 billion to 2.1 billion. double stores decimal numbers and is the default choice for anything with a fractional part, like prices or measurements. boolean can only ever be true or false, which makes it perfect for yes/no conditions. char stores exactly one character, written in single quotes like 'A' — never double quotes.

To store a single character like 'A', you use the ____ type.

Java also has smaller and larger whole-number types for when int isn't the right fit: byte and short save memory for tiny numbers, while long is used for whole numbers bigger than int can hold — you mark a long literal with an L at the end. float is a smaller, less precise alternative to double, rarely used unless memory is tight.

long population = 8_000_000_000L;
byte smallNumber = 120;

Fields that belong to a class automatically get a default value if you don't initialize them — 0 for numeric types, false for boolean, and a null character for char. Local variables declared inside a method, however, do not get a default value: Java's compiler forces you to assign one before you can use the variable, which helps catch bugs early.

A local variable declared inside a method automatically gets a default value, like 0, if you never initialize it.

Which primitive type would you use to store whether a light switch is on or off?