changes to the methods, which were loading the database from the file,
made them synchronize method inorder to handle concurrency,
change in the removeinRange method
Using Iterator and while loop.
			 * In this method you can remeove the entries
			 * while iterating through it.
			 *  The previous for loop will through
			 *   java.util.ConcurrentModificationException 
			 *   if you remove while iterating.