Data Types in Java

Data Types in Java

1. Two Families (big picture)

Primitive (value in box: fast, lowercase) vs Reference (address of object: String, arrays, classes). Beginners master primitives first.

2. 8 Primitives (exam table — memorize size + example)

Type	Size	Range / Use	Example
byte	1 byte	-128 to 127	byte b = 100;
short	2 bytes	-32k to 32k	short s = 1000;
int	4 bytes	~±2 billion (default integer)	int marks = 87;
long	8 bytes	huge (needs L)	long pop = 1400000000L;
float	4 bytes	decimal (needs f)	float pi = 3.14f;
double	8 bytes	decimal default	double x = 3.14159;
char	2 bytes	single Unicode char	char c = 'A';
boolean	1 bit-ish	true/false only	boolean pass = true;

Default: int for whole numbers, double for decimals. So long needs L, float needs f.

3. Code — See Defaults Bite

public class Types {
    public static void main(String[] args) {
        int marks = 87;            // default int — fine
        // float f = 3.14;         // ERROR! 3.14 is double
        float f = 3.14f;           // ok with f
        long big = 9000000000L;    // needs L (bigger than int range)
        char c = 'A';
        System.out.println((int) c); // 65 — chars are numbers!
        boolean pass = marks >= 40;
        System.out.println(pass);    // true
    }
}

4. Reference Preview (next topics)

String name = "Asha"; int[] arr = {1,2}; — these hold addresses, default null, compare with .equals() (not ==).

5. Exam Points

• 8 primitives table + defaults (L, f) — 5-7 marks, very frequent.
• int vs long, float vs double traps — 3 marks, frequent.
• char as number ((int)'A' = 65) — 2-mark favourite.