Question

I’m sure there’s a simple solution to this but it’s got me stuck so hopefully someone can give me a hand. I’ve got multiple lines of input that look like this:

FooABC
Foo XYZ123
FooFgh

I need a regex (in Java) that will give me:

ABC
XYZ123
Fgh

The best I’ve come up with so far is:

[^Foo\s?].*$

Which I thought was working until I noticed that it was removing the capital F from Fgh. Is there any way I can make it exactly ignore the first three characters and one or more whitespace characters then just capture everything else?

EDIT / CLARIFICATION

I should have said that I can’t use substring / replace or any of the things I would normally do in this situation because this regex will be fed into deployed code that can’t currently be updated. What the code is doing is this:

Pattern pattern = Pattern.compile( regex );
Matcher matcher = pattern.matcher( data );
matcher.find();
String extracted = matcher.group();

and it’s then using the extracted string as a key for a look up. So it has to extract the key in one pass.

Answer 1

Replace

^Foo\s*

with an empty string. Use .{3} if you need 3 arbitrary characters instead of Foo.

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If you need to use match instead of replace, you need to use a capture group:

^Foo\s*(.*)$

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The [^Foo\s?] is a character class ([...]) to match any characters except (^) an F, a o, a whitespace (\s) or a question mark ?. That’s why the F in Fgh is also matched. If you want a grouping bracket, use (?:...).