The Least Knowledge Principle

The principle of least knowledge guides us to reduce the interaction between object to just only few close friend the class itself. Don't try to be a close friend to all other class in the system. When you designing a system which composes of many classes and sub classes, you gotta be careful that one class should only interacts with those close immediately close friend and try to make least coupling as much as you can. For one system that all class are tightly coupling ( one class has interactions to many classes) will increase the complexity of the system and boost up the cost of maintanance.