如何在实例化之前参数化通用类？

Question

I am loading the db-driver based on command line parameters like this:

Class driverClass = null;
try {
    driverClass = Class.forName(dbDriver);
catch(ClassNotFoundException e) {
    // Print error message here
}

Later I call driverClass.newInstance() .

How can I avoid the message

Class is a raw type. References to generic type Class<T> should be parameterized

If I try Class<Driver> the Class.forName part complains about a type mismatch:

Type mismatch: cannot convert from Class<capture#1-of ?> to Class<Driver>

This is weird, how can I parameterize the Class in the first line correctly?

Answer 1

If you do now know the exact class name, you can specify ? as a type meaning any class that extends Object :

Class<?> driverClass = Class.forName(dbDriver);

Answer 2

If I try Class the Class.forName part complains about a type mismatch

Well if you know the class name at compile time, why initialise the class using forName , just do this:

Class<Driver> driverClass = Driver.class;

If you don't know the class name at compile time, you can simply put a ? as the type parameter:

Class<?> driverClass = null;