I know of no simple methods that fit this bill. The only solution I can think of for simplifying the calling of a toString method on a 2-D array would be to create a wrapper class that held the 2-D array and create a toString override method that internally would use nested for-loops and a StringBuilder to build the String you desire.
Darryl's suggestion is a good one, but if you look at the code for Arrays.toString, you'll see that it uses a StringBuilder and a for-loop, and so Darryl's example still uses at its core nested for-loops.