that is a smart solve ,, i like it , i know that is don't best practice and there was more solutions is more readable than it's but this is a new practice and a new way for the solution for me, so i like it.
i know my english language is bad :)

a gap means that there are no prime numbers in between. think about it :)

JAVA :))
U can see test???
assertEquals(null, GapInPrimes.gap(6,100,110));
check plz:))

JAVA :))
U can see test???
assertEquals(null, GapInPrimes.gap(6,100,110));
check plz:))

test(StepInPrimesTest)
Fixed Tests
expected: but was:<[J@593aecec>
test1(StepInPrimesTest)
100 Random Tests
Test Passed
?????????