java interfaces and parameters types

Question

I'm trying to parameterize a generic type with an interface and Eclipse tells me that method abc() is not implemented for the type T. Of course it is not implemented since T is an interface, the program will figure out at runtime what T really is. So, if anyone could help me solve this, I would be really appreciate.

I have something like:

interface myInterface {
    String abc();
}

class myClass<T> implements myClassInterface<T> {
    String myMethod() {
        T myType;
        return myType.abc();   // here it says that abc() is not implemented for the type T
    }
}

public class Main{
      public static void Main(String[] arg) {
         myClassInterface<myInterface> something = new myClass<myInterface>;
      }
}

T is a generic type. Where's the connection to your interface? — Rabbit Guy, Aug 27 '16 at 12:00
[Bounded generic type](https://docs.oracle.com/javase/tutorial/java/generics/bounded.html) is what you need — Vladimir Vagaytsev, Aug 27 '16 at 12:01

score 3 · Accepted Answer · answered Aug 27 '16 at 11:59

3

As you have defined it T is of type Object. What you want instead is giving the compiler the hint that T is actually a type of myInterface. You do that by defining that T extends myInterface:

class myClass<T> implements myClassInterface<T extends myInterface>{
       String myMethod(){
            T myType;
            return myType.abc();
       }
}

answered Aug 27 '16 at 11:59

hotzst

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I tried: class myClass implements myClassInterface and it worked. Thank you ! – Lexy Aug 27 '16 at 12:26

java interfaces and parameters types

1 Answers1