simple java regex throwing illegalstateexception [duplicate]

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You need to invoke m.find() or m.matches() first to be able to use m.group.

  • find can be used to find each substring that matches your pattern (used mainly in situations where there is more than one match)
  • matches will check if entire string matches your pattern so you wont even need to add ^ and $ in your pattern.

We can also use m.lookingAt() but for now lets skip its description (you can read it in documentation).

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