Primitive Data Types

Two Families of Types

Primitive types (8 of them): store the actual value directly. byte, short, int, long, float, double, char, boolean.
Reference types: store a reference (address) to an object. String, arrays, classes, interfaces.

The Eight Primitives

Type	Size	Range / values	Default (fields)
`byte`	1 byte	-128 to 127	0
`short`	2 bytes	-32,768 to 32,767	0
`int`	4 bytes	about -2.1 billion to 2.1 billion	0
`long`	8 bytes	about -9.2 x 10^18 to 9.2 x 10^18	0L
`float`	4 bytes	~6-7 decimal digits precision	0.0f
`double`	8 bytes	~15-16 decimal digits precision	0.0
`char`	2 bytes	one Unicode character (0 to 65,535)	'\u0000'
`boolean`	-	`true` or `false`	false

All Primitives in Action

Example

public class Main {
    public static void main(String[] args) {
        byte level = 5;
        short year = 2025;
        int population = 1_400_000_000;   // underscores make big numbers readable
        long distanceToSunKm = 149_600_000L;
        float rating = 4.5f;
        double pi = 3.141592653589793;
        char grade = 'A';
        boolean isOpen = true;

        System.out.println(level + " " + year + " " + population);
        System.out.println(distanceToSunKm + " " + rating + " " + pi);
        System.out.println(grade + " " + isOpen);
    }
}

Output

5 2025 1400000000
149600000 4.5 3.141592653589793
A true

Tip: Use int for whole numbers and double for decimals unless you have a reason not to. Add L for long literals and f for float literals.