smart

I'm sure this is clever, but wow, it's awfully dense. If you were writing code for production, it would need a lot of comments!
But I think you were not writing for production.

Im gonna take this

OMG bro,you show me a new method to play this!That's so interesting!

What does this do? Please some comment or description.

Good, but the same regExp is evaluated twice on a given string which is inefficient for very long inputs.
That can be optimized.

Wow, You have just shown me that simple task can have awesome and unobvious solutions :)

Impressive. very nice.

Really clever !

Hi @steffan153, I'm a beginner in java and I've never seen "<<", could you explain ? The mentioned doc didn't enlighten me a lot... Thanks :)

for these regex ones I'm not quite sure I understand how they verify that one pair doesn't close before an inner pair is closed?

Bit shift is awesome. Nice job