Answer
Primitive Data Types in Java
Java has 8 primitive data types — the most basic data types, stored on the stack (not heap), not objects.
The 8 Primitive Types
| Type | Size | Default | Range | Example |
|---|---|---|---|---|
byte | 1 byte | 0 | -128 to 127 | byte b = 100; |
short | 2 bytes | 0 | -32,768 to 32,767 | short s = 1000; |
int | 4 bytes | 0 | -2B to 2B | int i = 50000; |
long | 8 bytes | 0L | -9.2Q to 9.2Q | long l = 9999999999L; |
float | 4 bytes | 0.0f | ±3.4×10³⁸ | float f = 3.14f; |
double | 8 bytes | 0.0 | ±1.7×10³⁰⁸ | double d = 3.14159; |
boolean | 1 bit | false | true/false | boolean flag = true; |
char | 2 bytes | 'null' | 0 to 65.535 | char c = 'A'; |
Examples
Java
byte age = 25;
short year = 2024;
int population = 1_400_000_000; // underscores for readability
long distance = 9_460_730_472_580_800L; // must end with L
float price = 9.99f; // must end with f
double pi = 3.141592653589793;
boolean isActive = true;
char grade = 'A';
System.out.println((int) 'A'); // 65 — char to int conversion
System.out.println((char) 66); // 'B' — int to char conversion
Primitives vs Wrapper Classes
Every primitive has a corresponding Wrapper class (object):
| Primitive | Wrapper |
|---|---|
int | Integer |
double | Double |
boolean | Boolean |
char | Character |
long | Long |
Java
// Autoboxing — primitive → object (automatic)
int primitive = 42;
Integer wrapped = primitive; // autoboxing
// Unboxing — object → primitive (automatic)
Integer obj = 100;
int value = obj; // unboxing
// Useful for collections (which need objects, not primitives)
List<Integer> numbers = new ArrayList<>();
numbers.add(1); // autoboxing — int → Integer
int n = numbers.get(0); // unboxing — Integer → int
Type Casting
Java
// Widening (automatic — no data loss)
int i = 100;
long l = i; // int → long (safe)
double d = l; // long → double (safe)
// Narrowing (explicit — possible data loss)
double pi = 3.14;
int truncated = (int) pi; // 3 — decimal part lost
long big = 1_000_000_000_000L;
int small = (int) big; // data loss — overflow!