20.10

java.lang.Double

THE PACKAGE JAVA.LANG

How many digits must be printed for the fractional part of

m

 or

a

? There must

be at least one digit to represent the fractional part, and beyond that as many, but

only as many, more digits as are needed to uniquely distinguish the argument

value from adjacent values of type

double

. That is, suppose that

x

 is the exact

mathematical value represented by the decimal representation produced by this

method for a finite nonzero argument

d

. Then

d

must be the

double

 value nearest

to

x

; or if two

double

 values are equally close to

x

, then

d

must be one of them

and the least significant bit of the significand of

d

must be

0

.

[This specification for the method

toString

 is scheduled for introduction in

Java version 1.1. In previous versions of Java, this method produces

Inf

 instead of

Infinity

 for infinite values. Also, it rendered finite values in the same form as

the

%g

 format of the

printf

 function in the C programming language, which can

lose information because it produces at most six digits after the decimal point.]

20.10.16

public static Double valueOf(String s)

throws NullPointerException, NumberFormatException

The string

s

 is interpreted as the representation of a floating point value and a

Double

 object representing that value is created and returned.

If

s

 is

null

, then a

NullPointerException

 is thrown.

Leading and trailing whitespace ( 20.5.19) characters in

s

 are ignored. The

rest of

s

 should constitute a

FloatValue

 as described by the lexical syntax rule:

FloatValue:

Sign

opt

 Digits

 .

Digits

opt

ExponentPart

opt

Sign

opt

.

Digits ExponentPart

opt

where

Sign

,

Digits

, and

ExponentPart

 are as defined in  3.10.2. If it does not have

the form of a

FloatValue

, then a

NumberFormatException

 is thrown. Otherwise,

it is regarded as representing an exact decimal value in the usual  computerized

scientific notation ; this exact decimal value is then conceptually converted to an

 infinitely precise  binary value that is then rounded to type

double

 by the usual

round to nearest rule of IEEE 754 floating point arithmetic. Finally, a new object

of class

Double

 is created to represent the

double

 value.

Note that neither

D

 nor

d

 is permitted to appear in

s

 as a type indicator, as

would be permitted in Java source code ( 3.10.1).

20.10.17

public boolean isNaN()

The result is

true

 if and only if the value represented by this

Double

 object is

NaN.

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