5.1

Kinds of Conversion

CONVERSIONS AND PROMOTIONS

which produces the output:

(int)12.5f==12

after float widening: 12.0

12.0*12==144.0

Math.sin(144.0)== 0.49102159389846934

5.1   Kinds of Conversion

Specific type conversions in Java are divided into six categories.

5.1.1   Identity Conversions

A conversion from a type to that same type is permitted for any type. This may

seem trivial, but it has two practical consequences. First, it is always permitted for

an expression to have the desired type to begin with, thus allowing the simply

stated rule that every expression is subject to conversion, if only a trivial identity

conversion. Second, it implies that it is permitted for a program to include redun 

dant cast operators for the sake of clarity.

The only permitted conversion that involves the type

boolean

 is the identity

conversion from

boolean

 to

boolean

.

5.1.2   Widening Primitive Conversions

The following 19 specific conversions on primitive types are called the

widening

primitive conversions

:

byte

to

short

,

int

,

long

,

float

, or

double

short

to

int

,

long

,

float

, or

double

char

to

int

,

long

,

float

, or

double

int

to

long

,

float

, or

double

long

to

float

 or

double

float

to

double

Widening primitive conversions do not lose information about the overall

magnitude of a numeric value. Indeed, conversions widening from an integral type

to another integral type and from

float

 to

double

 do not lose any information at

all; the numeric value is preserved exactly. Conversion of an

int

 or a

long

 value

to

float

, or of a

long

 value to

double

, may result in

loss of precision

 that is,

the result may lose some of the least significant bits of the value. In this case, the

54