it will be undecidable,
given a DFA, there is an algorithm to find language corresponding to given DFA, now upto this point every thing is decidable, now
problem is,
"given a regular language, whether there exist some string in this language containing an equal number of 0s and 1s ?"
according to rice's theorem it will be undecidable, since there is Tyes for {0, 1, 1100} and Tno for {0,1}