ch.randelshofer.fastdoubleparser

Class FastDoubleParser

java.lang.Object

ch.randelshofer.fastdoubleparser.FastDoubleParser

public class FastDoubleParser
extends java.lang.Object

This is a C++ to Java port of Daniel Lemire's fast_double_parser.

The code has been changed, so that it parses the same syntax as Double.parseDouble(String).

References:

Daniel Lemire, fast_double_parser, 4x faster than strtod. Apache License 2.0 or Boost Software License.

github.com

Daniel Lemire, fast_float number parsing library: 4x faster than strtod. Apache License 2.0.

github.com

Daniel Lemire, Number Parsing at a Gigabyte per Second. arXiv.2101.11408v3 [cs.DS] 24 Feb 2021

arxiv.org

Method Summary

Modifier and Type	Method and Description
static double	parseDouble(java.lang.CharSequence str) Returns a Double object holding the double value represented by the argument string str.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

parseDouble

public static double parseDouble(java.lang.CharSequence str)
                          throws java.lang.NumberFormatException

Returns a Double object holding the double value represented by the argument string str.

This method can be used as a drop in for method Double.valueOf(String). (Assuming that the API of this method has not changed since Java SE 16).

Leading and trailing whitespace characters in str are ignored. Whitespace is removed as if by the String.trim() method; that is, characters in the range [U+0000,U+0020].

The rest of str should constitute a FloatValue as described by the lexical syntax rules shown below:

FloatValue:

[Sign] NaN

[Sign] Infinity

[Sign] DecimalFloatingPointLiteral

[Sign] HexFloatingPointLiteral

SignedInteger

HexFloatingPointLiteral:

HexSignificand BinaryExponent

HexSignificand:

HexNumeral

HexNumeral .

0x [HexDigits] . HexDigits

0X [HexDigits] . HexDigits

HexSignificand:

HexNumeral

HexNumeral .

0x [HexDigits] . HexDigits

0X [HexDigits] . HexDigits

BinaryExponent:

BinaryExponentIndicator SignedInteger

BinaryExponentIndicator:

p

P

DecimalFloatingPointLiteral:

Digits . [Digits] [ExponentPart]

. Digits [ExponentPart]

Digits ExponentPart

ExponentPart:

ExponentIndicator SignedInteger

ExponentIndicator:

(one of)

e E

SignedInteger:

[Sign] Digits

Sign:

(one of)

+ -

Digits:

Digit {Digit}

HexNumeral:

0 x HexDigits

0 X HexDigits

HexDigits:

HexDigit {HexDigit}

HexDigit:

(one of)

0 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F

Parameters:

str - the string to be parsed

Returns:

the parsed double value

Throws:

java.lang.NumberFormatException - if the string can not be parsed