Thank you so much! it make sence now...i got it!

I also tried this situation...not useful~

if(a.length == 0 || a == null || b.length == 0 || b == null){
return false;
}

it also says "expected:<false> but was:<true>"

I think i have same problem with you..have you passed later? what did you do?

[JAVA]
I can pass all cases except case 4, which length of int[] a and int[] b both 0. i've already checked for this situation at the first time as the code:

if(a.length == 0 || b.length == 0){
return false;
}

but it didn't work!!
isn't it right? did i miss something?