Primitive Data Types in Java

Java has eight primitive types. They store simple values directly rather than object references.

Type	Size	Typical purpose
`byte`	8 bits	Small signed integers, binary data
`short`	16 bits	Small signed integers
`int`	32 bits	Default integer type
`long`	64 bits	Large signed integers
`float`	32 bits	Single-precision floating point
`double`	64 bits	Default floating-point type
`char`	16 bits	One UTF-16 code unit
`boolean`	JVM-dependent storage	`true` or `false`

Integer types

All four integer types are signed two’s-complement values:

byte small = 100;
short count = 20_000;
int population = 1_000_000;
long distance = 9_000_000_000L;

The L suffix marks a long literal. Underscores can improve readability inside numeric literals.

Floating-point types

1 2	float ratio = 0.75F; double average = 12.345;

Floating-point values follow IEEE 754 and cannot represent every decimal fraction exactly. Use BigDecimal for exact decimal arithmetic such as financial calculations.

char and Unicode

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char letter = 'A';
char newline = '\n';
char symbol = '\u03A9';

A char is one UTF-16 code unit, not necessarily a complete user-perceived character. Supplementary Unicode characters require a surrogate pair or code-point APIs.

boolean

1 2	boolean enabled = true; boolean finished = false;

Java does not implicitly convert numbers to Boolean values.

Defaults and local variables

Instance and static fields receive defaults: numeric primitives become zero, char becomes \u0000, and boolean becomes false. Local variables do not receive automatic defaults and must be assigned before use.

Each primitive has a wrapper class such as Integer, Long, Double, and Boolean, useful for generics, nullable values, and utility methods.