Variables and Data Types
Variables
Variables are memory spaces where we temporarily store data. Imagine them as “containers” labeled with a name and a data type.
int age = 25;
age = 30; // We can change its value at any time
Primitive Data Types
Java has 8 built-in basic data types:
1. Integers (Numbers without decimals)
| Type | Size | Range |
|---|
byte | 8 bits | -128 to 127 |
short | 16 bits | -32,768 to 32,767 |
int | 32 bits | ~-2 billion to ~2 billion |
long | 64 bits | Huge range (use ‘L’ at the end: 100L) |
2. Floating-point numbers (Numbers with decimals)
| Type | Size | Use |
|---|
float | 32 bits | Single precision (use ‘f’ at the end: 3.14f) |
double | 64 bits | Double precision (standard for decimals) |
3. Characters
char: Stores a single Unicode character (use single quotes: 'a').
4. Booleans
boolean: Can only be true or false.
Summary table
| Type | Group | Size | Range |
|---|
boolean | Logical | 1 bit | true or false |
byte | Integer | 8 bits | -128 to 127 |
char | Character | 16 bits | ’\u0000’ to ‘\uffff’ |
int | Integer | 32 bits | -2,147,483,648 to 2,147,483,647 |
double | Real | 64 bits | ~1.7e308 |