What is the best way for constructing a never matching `Pattern`?

Asked Nov 13 '18 at 13:08

Active Nov 13 '18 at 13:08

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An existing interface requires a Pattern instance for matching labeled items, but I want to ignore all items at some point. Pattern has no constant NO_MATCH, DISCARD_ALL or something similar.

Currently I use this:

Pattern.compile("^.^")

Is there a better solution?

(PS, sadly, java's regex engine lacks support for backtracking controls like (*FAIL).)

asked Nov 13 '18 at 13:08

Dávid Horváth

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Actually, `(?!)` acts as `(*FAIL)`, it is used in constructions like `(*SKIP)(?!)`, as a synonym of `(*SKIP)(*FAIL)`. – Wiktor Stribiżew Nov 13 '18 at 13:11
@WiktorStribiżew Thanks for this information. To the duplication flag: I have seen the previous question, but my question is java related; so, for example, I would be very happy a dedicated `Pattern` instance for unmatching. – Dávid Horváth Nov 13 '18 at 13:18
Use `(?!)` and it will never match anything. – Wiktor Stribiżew Nov 13 '18 at 13:20

What is the best way for constructing a never matching `Pattern`?

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