Summary of Variables

When you declare a variable, you explicitly set the variable's name and data type. The Java programming language has two categories of data types: primitive and reference. This table shows all of the primitive data types:

Keyword Description Size/Format
(integers)

byte Byte-length integer 8-bit two's complement

short Short integer 16-bit two's complement

int Integer 32-bit two's complement

long Long integer 64-bit two's complement

(real numbers)

float Single-precision floating point 32-bit IEEE 754

double Double-precision floating point 64-bit IEEE 754

(other types)

char A single character 16-bit Unicode character

boolean A boolean value (true or false) true or false

Reference types are arrays, or names of classes or interfaces.
The variable declaration also implicitly sets the variable's scope, and you may optionally provide an initial value for the variable within its declaration. The value of a final variable may not change after it's initialized.
Note: bit - short for binary digit, the smallest unit of information on a machine. The term was first used in 1946 by John Tukey, a leading statistician and adviser to five presidents. A single bit can hold only one of two values: 0 or 1. More meaningful information is obtained by combining consecutive bits into larger units.

Keyword	Description	Size/Format
(integers)
`byte`	Byte-length integer	8-bit two's complement
`short`	Short integer	16-bit two's complement
`int`	Integer	32-bit two's complement
`long`	Long integer	64-bit two's complement
(real numbers)
`float`	Single-precision floating point	32-bit IEEE 754
`double`	Double-precision floating point	64-bit IEEE 754
(other types)
`char`	A single character	16-bit Unicode character
`boolean`	A boolean value (`true` or `false`)	true or false