In my opinion, this solution is too difficult to read, therefore it is difficult for support too :)
But it works :)

Seems it is not a good advice. Please look https://stackoverflow.com/a/4042464

As always, there's a trade-off between processing power and memory.

+1 for the error message :p

I know. I was change solution but this solution I can't change :) I saw that trouble after I change my solution.

You're right- I should have had the last line return null but my solution made it through the test cases so I didn't look too closely at it :/

You report finding the needle when there is no needle...

IllegalArgumentException would be more appropos.
Either that or "not found"

Nice math. Why not just make n a long instead of an int?

Where you say "if ( kk == 1+8n ) return true; else return false;" you could simplify to "return kk == 1+8n"

thank's for your notice!
unfortunately, i'm deep in other task now(( ..to solve exactly this.

yeah, that would be better...
thank you!

Your main loop is nice. The isOpposite( ) method could use some clean up.

dist.toArray(new String[dist.size()]) would save you an allocation.

path.toArray(new String[path.size()]) would save you an allocation.