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https://issues.apache.org/jira/browse/LANG-1040?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14522991#comment-14522991
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Bruno P. Kinoshita commented on LANG-1040:
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> Or we define exactly what we accept by specifying a grammar in the Javadocs.
I think that's probably the best scenario for users.
I tried using the following code found in [this StackOverflow
answer|http://stackoverflow.com/questions/1102891/how-to-check-if-a-string-is-a-numeric-type-in-java]
to replace isNumber, and then executed the NumberUtilsTest#testIsNumber test
method:
{noformat}
try {
Double.parseDouble(str);
} catch (NumberFormatException e) {
return false;
}
return true;
{noformat}
And the test failed with:
{noformat}
java.lang.AssertionError: Expecting true for isNumber/createNumber using
"-0xABC123" but got false and true
{noformat}
Using the Regex version:
{noformat}
return str.matches("-?\\d+(\\.\\d+)?");
{noformat}
Results in:
{noformat}
java.lang.AssertionError: Expecting true for isNumber/createNumber using
".12345" but got false and true
{noformat}
And the final example:
{noformat}
NumberFormat formatter = NumberFormat.getInstance();
ParsePosition pos = new ParsePosition(0);
formatter.parse(str, pos);
return str.length() == pos.getIndex();
{noformat}
Gives:
{noformat}
java.lang.AssertionError: Expecting true for isNumber/createNumber using
"1234E+5" but got false and true
{noformat}
Maybe we can fix this issue by enhancing the docs with a grammar and some
examples of what the method can and cannot handle?
> 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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