Question

I am trying to store a variable with the data type DataType<? extends T>.
I have tried with DataType<? extends T> var; but it seems not to work.

Storing as DataType<?> var; works, but I can’t cast to DataType<? extends T>.

Is there any possibility to get it working?

EDIT:

Perhaps it will be easier, when I give more information.

I use the AndroidHttpClient in an AsyncTask, which executes different requests in background while showing a ProgressDialog.
I am looking for a simple implementation, which may allow me to transfer ResponseHandler as parameters for the method execute of the HttpClient implementation.

Answer 1

EDIT

The problem is the parameterized type is declared in the method. You cannot store the parameter with the types you want as a class data member, because there is no way to know the type in the class declaration, because the type information is only determined when the method is called.

public class Snippet<T> {

    private final ResponseHandler<? extends T> var;

    public Snippet(ResponseHandler<? extends T> var) {
        super();
        this.var = var;
    }


    public <U> U execute(ResponseHandler<? extends U> responseHandler) {
        // This class is generic wrt to T, but this method is generice wrt to U.
        // You cannot store the variable passed in here in a data member
        // because the type cannot possible be known at compile time, as it
        // depends on client code calling this method.
        return null;
    }
}