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Date: Fri, 12 Sep 2014 12:38:34 +0000 (UTC)
From: "Duncan Jones (JIRA)" <jira@apache.org>
To: issues@commons.apache.org
Message-ID: <JIRA.12716767.1401186293000.18172.1410525514037@Atlassian.JIRA>
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Subject: [jira] [Comment Edited] (LANG-1018) NumberUtils.createNumber(final
 String str)  Precision will be lost
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    [ https://issues.apache.org/jira/browse/LANG-1018?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14131473#comment-14131473 ] 

Duncan Jones edited comment on LANG-1018 at 9/12/14 12:38 PM:
--------------------------------------------------------------

Closely related discussion found at LANG-693.

The problem is that [Java allocates 23-bits|http://stackoverflow.com/a/13543600/474189] for the [significand|http://en.wikipedia.org/wiki/Significand] in a float. This guarantees *6* decimal figures in the significand, not 7. The fix for LANG-693 checks for the wrong values.

I need to do some more investigation, but I see two solutions:

# Leave the simple test in place, but change to {{< 7}} and {{< 16}} for floats and doubles respectively. And change it to count the size of the significand, not just the decimal places.
# Change the approach and calculate the bit-length of the significand and switch types based on that. 


was (Author: dmjones500):
Closely related discussion found at LANG-693.

The problem is that [Java allocates 23-bits|http://stackoverflow.com/a/13543600/474189] for the [significand|http://en.wikipedia.org/wiki/Significand] in a float. This guarantees *6* decimal figures in the significand, not 7. The fix for LANG-693 checks for the wrong values.

I need to do some more investigation, but I see two solutions:

# Leave the simple test in place, but change to {{< 7}} and {{< 16}} for floats and doubles respectively.
# Change the approach and calculate the bit-length of the significand and switch types based on that. 

> NumberUtils.createNumber(final String str)  Precision will be lost
> ------------------------------------------------------------------
>
>                 Key: LANG-1018
>                 URL: https://issues.apache.org/jira/browse/LANG-1018
>             Project: Commons Lang
>          Issue Type: Bug
>          Components: lang.math.*
>    Affects Versions: 3.3.2
>         Environment: windows 7
>            Reporter: sydng
>             Fix For: Patch Needed
>
>
> With commons-lang 3.2.2:
> NumberUtils.createNumber("-160952.54");
> The result is "-160952.55".
> Should not be based on the length of the decimal point number to judge whether the floating point number.
> Using the method (createFloat(str)) of dealing with the valid number greater than seven Numbers will cause accuracy loss.
> The source code is as follows:
> {code:java}
> try {
>             if(numDecimals <= 7){// If number has 7 or fewer digits past the decimal point then make it a float
>                 final Float f = createFloat(str);
>                 if (!(f.isInfinite() || (f.floatValue() == 0.0F && !allZeros))) {
>                     return f;
>                 }
>             }
>         } catch (final NumberFormatException nfe) { // NOPMD
>             // ignore the bad number
>         }
>         try {
>             if(numDecimals <= 16){// If number has between 8 and 16 digits past the decimal point then make it a double
>                 final Double d = createDouble(str);
>                 if (!(d.isInfinite() || (d.doubleValue() == 0.0D && !allZeros))) {
>                     return d;
>                 }
>             }
>         } catch (final NumberFormatException nfe) { // NOPMD
>             // ignore the bad number
>         }
>         return createBigDecimal(str);
>     }
> {code}


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