Eng 6095 index with address

Pass eecheck on local machine, but haven't check the result of Junit test.

I worry about how to deconstruct Key and Data: is the default deconstructor enough?

After refining the code, the next step is to append address to KeyType other than IntsKey.
The validation could be extended a little. 
Can you use the "indexed count" API to validate that the index contains the expected number of remaining tuples -- like by asking for the number of tuples with indexed values >= 0?