Is there an alternative to StringUtils.isNumeric that does what I mean?

NumberUtils.isNumber is deprecated.

Your should use

NumberUtils.isCreatable

or

NumberUtils.isParsable

All of them support a decimal point value:

• NumberUtils.isCreatable support hexadecimal, octal numbers, scientific notation and numbers marked with a type qualifier (e.g. 123L). Not valid octal values will return false (e.g. 09). If you want get its value, you should use NumberUtils.createNumber.
• NumberUtils.isParsable only support 0~9 and decimal point (.), any other character (e.g. space or other anything) will return false.

By the way, StringUtils.isNumeric's implement has some different between commons-lang and commons-lang3. In commons-lang, StringUtils.isNumeric("") is true. But in commons-lang3, StringUtils.isNumeric("") is false. You can get more info by documents.

Try isNumber(String) from org.apache.commons.lang.math.NumberUtils.

Checks whether the String [is] a valid Java number.

Valid numbers include hexadecimal marked with the 0x qualifier, scientific notation and numbers marked with a type qualifier (e.g. 123L).

Null and empty String will return false.

UPDATE -

isNumber(String) is now deprecated. Use isCreatable(String) instead.

Thank you eav for pointing it out.