LRU Cache implemented in Java

Your cache should store simple key/value strings of length up to 10 characters. It should also have a customizable upper bound to the number of keys that can be stored in the cache at any time. You do not have to be thread safe.

Possible Inputs:

BOUND : Set the upper bound. If the cache size is currently greater than this number, then extra entries must be removed following the LRU policy

SET : Set the value of this key

GET : Get the value of this key and prints to stdout.

PEEK : Gets the value of the key but does not mark it as being used. Prints the value to standard out.

DUMP : Prints the current state of the cache as a list of key/value pairs in alphabetical order by key.

Input Format:

First line of input contains an integer N,the number of commands.

The following N lines each describe a command.

Note: The first command will always be BOUND.

Output Format:

Print the appropriate outputs for GET , PEEK and DUMP commands. In case for GET/PEEK command if the key does not exist in the cache just output the string "NULL"(quotes are for clarity).

Sample Input

8 BOUND 2 SET a 2 SET b 4 GET b PEEK a SET c 5 GET a DUMP

Sample Output

4 2 NULL b 4 c 5

Constraints:

Total number of lines in input will be no more than 1,000,000(10^6)