To express the entire implementation of a control-framework application in a single class, thereby encapsulating everything that�s unique about that implementation. Inner classes are used to express the many different kinds of action( ) necessary to solve the problem. the implementation is completely hidden and can be changed with impunity. 2. Inner classes keep this implementation from becoming awkward, since you�re able to easily access any of the members in the outer class. Without this ability the code might become unpleasant enough that you�d end up seeking an alternative.