Primitive and Reference Types¶

Primitive Types¶

Java has 8 primitive data types that store simple values directly in memory.

Type	Size	Default Value	Range	Example
`byte`	1 byte (8 bits)	0	-128 to 127	`byte b = 100;`
`short`	2 bytes (16 bits)	0	-32,768 to 32,767	`short s = 30000;`
`int`	4 bytes (32 bits)	0	-2^31 to (2^31)-1	`int i = 100000;`
`long`	8 bytes (64 bits)	0L	-2^63 to (2^63)-1	`long l = 100000L;`
`float`	4 bytes (32 bits)	0.0f	~±3.4E38 (7 decimal digits precision)	`float f = 3.14f;`
`double`	8 bytes (64 bits)	0.0	~±1.8E308 (15 decimal digits precision)	`double d = 3.14159;`
`char`	2 bytes (16 bits)	'\u0000'	Unicode characters (0 to 65,535)	`char c = 'A';`
`boolean`	1 bit (virtual)	false	true or false	`boolean b = true;`

Reference types store references (addresses) to objects in memory, unlike primitive types that store values directly.

String: Represents a sequence of characters.
```
String str = "Hello, World!";
```
Arrays: Collections of elements of the same type.
```
int[] numbers = {1, 2, 3};
```

Classes and Objects: Custom data types representing real-world entities.

class Person {
    String name;
}
Person p = new Person();

Interfaces: Contracts that classes can implement.
```
interface Animal {
    void sound();
}
```

Enums: Special classes that define a set of constants.

enum Day {
    MONDAY, TUESDAY, WEDNESDAY;
}

Wrapper Classes: Used to convert primitive types into objects (auto-boxing/unboxing).

Aspect	Primitive Types	Reference Types
Storage	Store actual values.	Store references to objects in memory.
Memory Allocation	Stored in stack memory.	Stored in heap memory.
Default Values	Zero/false equivalents.	`null` for uninitialized references.
Examples	`int`, `char`, `boolean`.	`String`, Arrays, Classes, Interfaces, etc.