The time complexity of any isEmpty() method implementation should be
O(1) whereas some implementations of size() can be O(n). Thus, using
this rule provides performance benefits.
jSparrow Cleanup

Change-Id: I62c6091f4b18a83dcd3acde701b116bc8c3ec27b
Signed-off-by: Ardit Ymeri <ardit.ymeri@splendit.at>