Generic Type From Enum & The Builder Pattern

Generic Type From Enum & The Builder Pattern

I'm trying to create a builder pattern that uses generics to provide type
checking on some of the methods. Currently I have the following working:
ParameterBuilder.start(String.class).setName("foo").setDefaultValue("Hello").build();
ParameterBuilder.start(Integer.class).setName(bar).setDefaultValue(42).build();
ParameterBuilder.start(Boolean.class).setName(bar).setDefaultValue(false).build();
Using the code:
public class ParameterBuilder<T> {
private String name;
private T defaultValue;
public static <T2> ParameterBuilder<T2> start(Class<T2> type) {
return new ParameterBuilder<T2>();
}
// Other methods excluded for example
}
So the type of the input for the setDefaultValue method is defined by
what's passed into the start method, just as I want.
But now I want to extend what's being passed into start() to contain a
little more information. Essentially I want to pass in a "type" for the
parameters I creating. Sometimes these parameters will be things like
"email", "url" etc. The default value will still be of a known type
(String in those cases), so I'd like to have something like:
ParameterBuilder.start(EMAIL).setName("email").setDefaultValue("foo@bar.com").build();
ParameterBuilder.start(URL).setName("website").setDefaultValue("http://www.somewhere.com").build();
Where at the moment EMAIL & URL are enums, containing amongst other things
- the class of the default value. But if I go down this route, how would I
instantiate the parameter builder?
public static <T2> ParameterBuilder<T2> start(ParameterType paramType) {
Class<T2> type = paramType.getTypeClass();
// How do I instantiate my ParameterBuilder with the right type?
}
If it can't be done using enums (which I can see being the case), does
anyone have a suggestion for a different solution?