Why a surrogate java regexp finds hyphen-minus -

Question

I am trying to find why this regex in JAVA ([\\ud800-\\udbff\\udc00-\\udfff]) used in replaceAll(regexp,\"\") is removing also the hyphen-minus charac

Answer 1

If you make the range

[\ud800-\udfff]

or

[\ud800-\udbff\udbff-\udfff]

it will leave the hyphen untouched. Seems like a bug to me.

Note there is no reason for the double range, in your example \udc00 is just the next code point after \udbff so you could skip that. If you make the two ranges overlap one or more code points, it works again, but you could just as well leave it out (see my first example above).