Formal parameters and return value issues

Problems with formal parameters :

    Formal parameters are primitive types and have no effect on actual parameters (simple)

    Formal parameters are reference types :

        class (normal class)         abstract class         interface

 

Return value :

    The return value is a basic type : just use the corresponding basic type to receive data!

    The return value is a reference type :

    Class (concrete class): what is required is an object of that class

        Abstract class : The result of need is to need a subclass object of the current abstract class Abstract class polymorphism 

Formal parameters are reference types :

Reference type : is an abstract class

The formal parameter is an abstract class : what this block needs is a subclass object of the abstract class (abstract class polymorphism ...)