Java · Chapter 8 of 42

Java Data Types

Java has two categories of data types: primitive types (byte, short, int, long, float, double, char, boolean) and reference types (objects, arrays, Strings).

Each primitive type has a fixed size defined by the Java specification, unlike C where sizes are platform-dependent.

Syntax

int a;
double b;
char c;
boolean d;

Primitive types

int (4 bytes) and double (8 bytes) are the most commonly used numeric types. byte, short and long provide other integer ranges, float is a single-precision decimal, char stores a single 16-bit Unicode character, and boolean stores true/false.

Reference types

String, arrays, and custom classes are reference types — they store a reference to an object in memory rather than the value itself.

Example 1 (java)

public class Main {
  public static void main(String[] args) {
    int a = 5;
    double b = 5.5;
    char c = 'A';
    boolean d = true;
    System.out.println(a + " " + b + " " + c + " " + d);
  }
}

Output

5 5.5 A true

Four primitive types are declared, initialized and printed.

Key points

Primitive types include int, double, char, boolean, byte, short, long, float.
Reference types include String, arrays and objects.
Primitive sizes are fixed by the Java spec, not the platform.
boolean stores only true or false.

💡 Note: Java has no unsigned integer types except char, which behaves like an unsigned 16-bit value.

Java Data Types

Primitive types

Reference types

Key points

📝 Quick Quiz