Q:

What is a supertype method?

I have googled couple of times but still can't understand the supertype method. Can anyone please explain what is this?

A:

There is a notion of supertype and subtype in OOPS, In java  this kind of relationship is implemented by inheritance i.e. using extends keyword:
class A {} // super class
class B extends A {} //sub class

Any member (fields, methods) declared in super class is to be called supertype.
Therefore in above context if class A has method like 
class A {
   void set()
}

Set is supertype method for class B.
However, notice that if there is another class say C: 
class C {
    void set()        
}

Then set() method is not supertype for C class because there is no relationship between class A and class C (relationship is created by extends keyword, for inheritance).

