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https://issues.apache.org/jira/browse/LANG-1040?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14245002#comment-14245002
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Sebb commented on LANG-1040:
----------------------------
I think "Java number" probably means a number that is valid as a Java numeric
literal.
If this is the case, then it is trivial to determine whether a particular
sequence of characters should pass the isNumber() test.
i.e. see if the Java compiler accepts it as a long/double/etc. initialiser.
> Javadoc for NumberUtils.isNumber() are not clear enough
> -------------------------------------------------------
>
> Key: LANG-1040
> URL: https://issues.apache.org/jira/browse/LANG-1040
> Project: Commons Lang
> Issue Type: Bug
> Components: lang.math.*
> Affects Versions: 3.3.2
> Reporter: Duncan Jones
> Fix For: Discussion
>
>
> The Javadocs for {{NumberUtils.isNumber()}} do not clearly define what a
> valid number is. The current trunk documentation states:
> {quote}Checks whether the String a valid Java number.
> Valid numbers include hexadecimal marked with the 0x or 0X qualifier, octal
> numbers, scientific notation and numbers marked with a type qualifier (e.g.
> 123L).
> Non-hexadecimal strings beginning with a leading zero are treated as octal
> values. Thus the string 09 will return false, since 9 is not a valid octal
> value. However, numbers beginning with 0. are treated as decimal.
> Null and empty String will return false.{quote}
> In other Jira issues, I've seen people suggest that a number if valid if it
> can be used when assigning to a suitable Java type. E.g. {{"FOO"}} is a valid
> number if {{long x = FOO}} is valid (where {{long}} might be another numeric
> type). If this is the case, we should state it.
> Alternatively, the definition could be in terms of what is accepted by
> {{createNumber()}}.
> Or we define exactly what we accept by specifying a grammar in the Javadocs.
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