Java: Class-type parametrized by interface implementations

Question

Let's say I have an interface

interface I {}

and two implementations thereof, class A implements I {} and class B implements I {} Now I would like to write a generic method which accepts a class-type parameter bounded by "Implements interface I", e.g.

boolean <T> isOK ( Class<T extents I> cl ) {
    switch ( cl ) {
       case A.class: return true ;
       case B.class: return false;
    }
}

How to do that?

by the way there is no need for T -- the declaration boolean isOK ( Class<? extents I> cl ) would be equivalent — newacct
– newacct, Commented Jul 15, 2018 at 1:43

khelwood · Accepted Answer · 2018-07-14 13:41:48Z

1

I think you mean something like:

public <T extends I> boolean isOK(Class<T> cl) {
   ...
}

The qualifiers for the generic type go at the point the generic type is declared, which is the first triangular brackets, not the second.

Also you can't switch on a Class, you'd have to use something else to examine it, such as an if statement.

answered Jul 14, 2018 at 13:41

khelwood

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