136 itself isn't prime though. You're looking for prime numbers with exactly 3 prime permutations (not including itself).

error by null

Stop pulling your hair for this one, it seems at some point the test for null wasn't there (so this code passed the existing tests) and this isn't marked now as a not valid solution (it happens from time to time in CW, solutions not being revalidated).

I wrote exactly the same thing but they showed an error

i even copied this code exactly :v

How comes your code is not throwing NullPointerException ?

NPE ?

What about null value. This will throw an exception : java.lang.NullPointerException

NPE :]

This would only pass the "basic" test but not the other 2. How can this be an accepted solution?

Exception in thread "main" java.lang.NullPointerException

How did this solution pass for null values?

I did the exact same, and it gave me 2 failures, had to do a notNull check before if-statement.

That will throw NPE in case null element in the array.