Data-Types

Java supports two categories of data types:

• Primitive Data Types: Store values directly, fixed size.
• Non-Primitive (Reference/Object) Data Types: Store references to objects, flexible size and behaviors.

---

Primitive Data Types

Primitive data types are predefined by Java and named by a reserved keyword and it can't devide more further.

Type	Size (bits)	Default Value	Range	Description	Example
byte	8	0	-128 to 127	Smallest integer type	byte b = 100;
short	16	0	-32,768 to 32,767	Small integer	short s = 2000;
int	32	0	-2,147,483,648 to 2,147,483,647	Default integer type	int n = 250000;
long	64	0L	-9,223,372,036,854,775,808 to 9,223,372,036,854,775,807	Large integer type	long m = 250000L;
float	32	0.0f	1.4e-45 to 3.4e+38	Single precision floating-point	float x = 2.3f;
double	64	0.0d	4.9e-324 to 1.8e+308	Double precision floating-point	double y = 5.7d;
char	16	'\u0000'	Unicode: 0 to 65,535	Single character (Unicode support)	char c = 'A';
boolean	1	false	true/false	Logic	boolean flag = true;

---

Primitive Groups

• Integer types: byte, short, int, long
• Floating-point types: float, double
• Character type: char
• Boolean type: boolean

---

Details & Notes

• byte/short/int/long: Same usage but for different numeric ranges to save memory.
• float: Ends with 'f' or 'F'. Precision up to 7 decimal digits.
• double: Ends with 'd' or 'D'. Precision up to 15 decimal digits.
• char: Can store any Unicode character, making it suitable for internationalization.
• boolean: Used for flags and logical control; only two possible values.

---

Non-Primitive (Reference) Data Types

Non-primitives, also called reference types, point to objects created by the programmer or provided by Java.It can divide more further.

Type	Description	Example
String	Sequence of characters (class)	String s = "Hello";
Array	Collection of similar elements	int[] arr = {1,2,3};
Class	User-defined or Java API class	MyClass obj = new MyClass();
Interface	Template for classes	Runnable r = new Thread();
Enum	Set of constants	enum Color {RED,GREEN}

---

Non-Primitive Details

• Strings are objects; many methods for text processing.
• Arrays can be multi-dimensional; element type must be uniform.
• Classes/Objects support attributes, methods, and inheritance.
• Interfaces/enums structure code and provide abstraction.

---

Comparison Table

Feature	Primitive Types	Non-Primitive Types
Memory Allocation	Stack	Heap (object), Stack (reference)
Supports methods	No	Yes
Extensible	No	Yes
Can be null	No	Yes
Size	Fixed	Variable
Used for	Simple values	Collections, objects, text, etc.

---

Example Code Block

// Primitives
int age = 21;
double salary = 65000.25d;
char grade = 'A';
boolean isActive = true;

// Non-primitives
String name = "Alex";
int[] marks = {85, 93, 78};
Person person = new Person("Alex");

---

Key Points

• Use primitives for basic values and calculations.
• Use non-primitives for complex data (objects, strings, arrays).
• Non-primitives provide extra functionality via methods and inheritance.
• Primitives are more memory efficient and faster for simple tasks.

---

This covers everything essential about Java's data types.