4.2.4

Floating Point Operations

TYPES, VALUES, AND VARIABLES

4.2.4   Floating Point Operations

Java provides a number of operators that act on floating point values:

The comparison operators, which result in a value of type

boolean

:

N

The numerical comparison operators

<

,

<=

,

>

, and

>=

( 15.19.1)

N

The numerical equality operators

==

 and

!=

 ( 15.20.1)

The numerical operators, which result in a value of type

float

 or

double

:

N

The unary plus and minus operators

+

and

( 15.14.3,  15.14.4)

N

The multiplicative operators

*

,

/

, and

%

( 15.16)

N

The additive operators

+

 and

 ( 15.17.2)

N

The increment operator

++

, both prefix ( 15.14.1) and postfix ( 15.13.2)

N

The decrement operator

, both prefix ( 15.14.2) and postfix ( 15.13.3)

The conditional operator

? :

 ( 15.24)

The cast operator, which can convert from a floating point value to a value of

any specified numeric type ( 5.4,  15.15)

The string concatenation operator

+

 ( 15.17.1), which, when given a

String

operand and a floating point operand, will convert the floating point operand

to a

String

 representing its value in decimal form (without information loss),

and then produce a newly created

String

 by concatenating the two strings

Other useful constructors, methods, and constants are predefined in the classes

Float

 ( 20.9),

Double

 ( 20.10), and

Math

 ( 20.11).

If at least one of the operands to a binary operator is of floating point type,

then the operation is a floating point operation, even if the other is integral.

If at least one of the operands to a numerical operator is of type

double

, then

the operation is carried out using 64 bit floating point arithmetic, and the result of

the numerical operator is a value of type

double

. (If the other operand is not a

double

, it is first widened to type

double

 by numeric promotion ( 5.6).) Other 

wise, the operation is carried out using 32 bit floating point arithmetic, and the

result of the numerical operator is a value of type

float.

If the other operand is

not a

float

, it is first widened to type

float

 by numeric promotion.

Operators on floating point numbers behave exactly as specified by IEEE 754.

In particular, Java requires support of IEEE 754

denormalized

 floating point num 

bers and

gradual underflow

, which make it easier to prove desirable properties of

particular numerical algorithms. Floating point operations in Java do not  flush to

zero  if the calculated result is a denormalized number.

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