code: public String get(String keyStr) throws DatabaseException {
  		String result = null;
  		DatabaseEntry key = new DatabaseEntry(stringToBytes(keyStr));
  		DatabaseEntry data = new DatabaseEntry();
  		if (db.get(null, key, data, LockMode.DEFAULT) 
  				== OperationStatus.SUCCESS) {
  		
  			result = bytesToString(data.getData());
  		}
  		return result;
      }
docs: retrieve the value assoicated with keyStr from persistant storage
  @param keyStr
  @return String value associated with key, or null if no key is found
  or an error occurs
  @throws DatabaseException