then if arr[2][] is interrogated then it should show data containing in arr[2][1] and arr[2][2] and arr[2][3]...., but it does not
Actually, there is no data in arr[2][], only another array. You can only check data when you fully dereference the array, and then only if you properly initialized the elements of the array. Just declaring an array does not initialize it with data. (See Java's initialization default values for the data type of the array.)
Also, in Java, the second-level arrays do not have to be the same size, so arr[2][] could hold a three-element array, while arr[1][] could hold a twelve element array.
Give a man a fish, he'll eat for one day. Teach a man to fish, he'll drink all your beer.
Cheers, Jeff (SCJP 1.4 all those years ago...)