Primitive Data Types in Java

Java has 8 primitive data types — they are the building blocks for all data in Java. Unlike objects, primitives directly store values in memory (not references), making them faster and more memory-efficient.

🎯Analogy: Primitive types are like different-sized cups. A byte is a shot glass (tiny), an int is a regular mug, and a double is a large bowl. Each holds a different amount and is used for different purposes.

8 primitive types — integer family (byte/short/int/long), floating-point (float/double), plus char and boolean

Type	Size	Range / Values	Default	Example
byte	1 byte	-128 to 127	0	byte b = 100;
short	2 bytes	-32,768 to 32,767	0	short s = 3000;
int	4 bytes	-2.1B to 2.1B	0	int i = 42;
long	8 bytes	Very large integers	0L	long l = 99L;
float	4 bytes	~6-7 decimal digits	0.0f	float f = 3.14f;
double	8 bytes	~15-16 decimal digits	0.0d	double d = 3.14159;
char	2 bytes	Unicode character (0–65535)	''	char c = 'A';
boolean	~1 bit	true or false	false	boolean b = true;

java

public class DataTypesDemo {
    public static void main(String[] args) {
        byte    population = 127;
        int     year       = 2024;
        long    worldPop   = 8_000_000_000L;
        double  pi         = 3.14159265358979;
        float   tax        = 0.18f;
        char    grade      = 'A';
        boolean isJavaFun  = true;

        System.out.printf("Year: %d | Pi: %.5f | Grade: %c | Fun: %b%n",
                          year, pi, grade, isJavaFun);
    }
}

Output

Year: 2024 | Pi: 3.14159 | Grade: A | Fun: true

Integer Types in Detail

java

// Check max/min values
System.out.println("int max:  " + Integer.MAX_VALUE);   // 2147483647
System.out.println("int min:  " + Integer.MIN_VALUE);   // -2147483648
System.out.println("long max: " + Long.MAX_VALUE);       // 9223372036854775807

// Integer overflow — wraps around!
int overflow = Integer.MAX_VALUE + 1;
System.out.println("Overflow: " + overflow);             // -2147483648

Output

int max:  2147483647
int min:  -2147483648
long max: 9223372036854775807
Overflow: -2147483648

⚠️Unlike Python, Java integers have a fixed size. If you exceed the range, it wraps around (overflow) — a common source of bugs. Use long for large values.

char and Unicode

java

char letter = 'A';
char unicode = 'A';    // Unicode for 'A'

System.out.println(letter);          // A
System.out.println((int) letter);    // 65 — ASCII value
System.out.println((char)(65 + 1));  // B — arithmetic on chars

Output

A
65
B

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