3.10.2

Floating Point Literals

LEXICAL STRUCTURE

3.10.2   Floating Point Literals

See  4.2.3 for a general discussion of the floating point types and values.

A

floating point literal

 has the following parts: a whole number part, a deci 

mal point (represented by an ASCII period character), a fractional part, an expo 

nent, and a type suffix. The exponent, if present, is indicated by the ASCII letter

e

or

E

 followed by an optionally signed integer.

At least one digit, in either the whole number or the fraction part, and either a

decimal point, an exponent, or a float type suffix are required. All other parts are

optional.

A floating point literal is of type

float

 if it is suffixed with an ASCII letter

F

or

f

; otherwise its type is

double

 and it can optionally be suffixed with an ASCII

letter

D

 or

d

.

FloatingPointLiteral:

Digits

 .

Digits

opt

ExponentPart

opt

FloatTypeSuffix

opt

.

Digits ExponentPart

opt

FloatTypeSuffix

opt

Digits ExponentPart FloatTypeSuffix

opt

Digits ExponentPart

opt

FloatTypeSuffix

ExponentPart:

ExponentIndicator SignedInteger

ExponentIndicator: one of

e E

SignedInteger:

Sign

opt

Digits

Sign: one of

+  

FloatTypeSuffix: one of

f F d D

The Java types

float

 and

double

 are IEEE 754 32 bit single precision and

64 bit double precision binary floating point values, respectively.

The details of proper input conversion from a Unicode string representation of

a floating point number to the internal IEEE 754 binary floating point representa 

tion are described for the methods

valueOf

 of class

Float

 ( 20.9.17) and class

Double

 ( 20.10.16) of the package

java.lang

.

The largest positive finite

float

 literal is

3.40282347e+38f

. The smallest

positive finite nonzero literal of type

float

 is

1.40239846e 45f

. The largest

positive finite

double

 literal is

1.79769313486231570e+308

. The smallest posi 

tive finite nonzero literal of type

double

 is

4.94065645841246544e 324

.

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