Java data types - Objects First with Java: A Practical Introduction Using BlueJ - page 503

APPENDIX
B

Java data types

Java's type system is based on two distinct kinds of type: primitive types and object types.

Primitive types are stored in variables directly, and they have value semantics (values are cop-
ied when assigned to another variable). Primitive types are not associated with classes and do
not have methods.

In contrast, an object type is manipulated by storing a reference to the object (not the object
itself). When assigned to a variable, only the reference is copied, not the object.

B.1 Primitive types

The following table lists all the primitive types of the Java language:

Type name Description Example literals

Integer numbers
byte

byte-sized integer (8 bit) 24 -2

short short integer (16 bit) 137 -119

int integer (32 bit) 5409 -2003

long long integer (64 bit) 423266353L 55L

Real numbers
float

single-precision floating point 43.889F

double-precision floating point 45.63

double 2.4e5

Other types
char a single character (16 bit) 'm' '?' '\u00F6'

boolean a boolean value (true or false) true false

Notes:

■ A number without a decimal point is generally interpreted as an int but automatically con-
verted to byte , short , or long types when assigned (if the value fits). You can declare a
literal as long by putting an L after the number. ( l , lowercase L , works as well but should be
avoided because it can easily be mistaken for a one ( 1 ).)
■ A number with a decimal point is of type double . You can specify a float literal by putting
an F or f after the number.
■ A character can be written as a single Unicode character in single quotes or as a four-digit
Unicode value, preceded by “ \ u ”.
■ The two boolean literals are true and false .