According to the Single Responsibility Principle, introduced by Robert C. Martin in his book "Principles of Object Oriented Design", a class should have only one responsibility:


____
If a class has more than one responsibility, then the responsibilities become coupled.

Changes to one responsibility may impair or inhibit the class' ability to meet the others.

This kind of coupling leads to fragile designs that break in unexpected ways when changed.

____

Classes which rely on many other classes tend to aggregate too many responsibilities and should be split into several smaller ones.

Nested classes dependencies are not counted as dependencies of the outer class.
