Difference between Bounded Type parameter (T extends) and Upper Bound Wildcard (? extends)

Question

I know that there was a similar question already posted, although I think mine is somewhat different...

Suppose you have two methods:

// Bounded type         


        

Answer 1

There are following three types of Wildcard usually used with Generic in JAVA. Each one is explained as below with example.

Upper-bounded Wildcard:

? extends T : In Upper bounded wildcard only T or its subtypes will be supported. For example we have an Animal class and have Dog , Cat as its subtypes. So following generic methods will only accept parameters of type Data, Data and Data

public static void add(Data animalData) {

}

Lower-bounded Wildcard:

? super T : In Lower-bounded wildcard only T or its super types will be supported. Same example we used for defining Lower-bounded Wildcard. Lets say we have Animal class as super or parent class and Dog as its child class. Now below method use Lower-bounded Wildcard and will only accept parameters of type

Data, Data and  Data