Main.java

interface I {
    public int x();
}

class IImpl {
    public int y() {
        return 3;
    }
}

class A implements I {
    public int x() {
        return 4;
    }
}

public class Main {
    public static <F,T> T convert(F obj) {
        //return (T)(Object)obj;
        return null;
    }
    public static void main(String[] args) {
        A a = new A();
        //IImpl i = (IImpl)(Object)a;
        IImpl i = convert(a);
        System.out.println(i.y());
    }
}