[2 days left] What’s wrong with your cloud strategy? Learn why multicloud solutions matter with Nimble Storage.Register Now

x
?
Solved

typesafe enum in generic class?

Posted on 2006-07-22
3
Medium Priority
?
1,516 Views
Last Modified: 2008-01-09
Hi everybody,

I have a question about Generics and Enums: The answer is either simple (about 1 line) or there is no answer...

I have a parameterized class which uses an Enum. I want to use "typesafe" Enum.valueOf, but it doesn't work...

looks sth. like this:

public class MyClass<FIELDS extends Enum> {
      protected Class<FIELDS> fieldClass;

      public MyClass() {
            Type[] ata = ((ParameterizedType)getClass().getGenericSuperclass()).getActualTypeArguments();
            this.fieldClass = (Class<FIELDS>) ata[0];
            ...
      }

      public void someMethod(String fieldName) {
            FIELDS f = Enum.valueOf(fieldClass, fieldName);
      }

This gives me a type safety warning in Eclipse 3.2.
Why?
Enum.valueOf is defined as
public static <T extends Enum<T>> T valueOf(Class<T> enumType, String name)

and I'm passing a parameter that is declared as "Class<FIELDS>". What do I have to do to get a return type of FIELDS?

To make this clear: My code works fine, but I just want to use as much typesafe programming as possible and avoid using '@SuppressWarnings("unchecked")' where possible!
 
Thanks for any hints!
0
Comment
Question by:Ronald112197
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
3 Comments
 
LVL 23

Accepted Solution

by:
Ajay-Singh earned 200 total points
ID: 17159768
> public class MyClass<FIELDS extends Enum>
should be

public class MyClass<FIELDS extends Enum<FIELDS>>
0
 
LVL 2

Author Comment

by:Ronald112197
ID: 17159794
ah, ok, thanks for the super fast answer :-)
(see, I know this would only be one line :-)

I have to admit that there might be a tiny piece of the Generics puzzle that I still don't fully understand which I'd like to call "self referencing parameters", like Class<T> and Enum<T>.
Oh well, I'll figure that out sooner or later :-)
0
 
LVL 23

Expert Comment

by:Ajay-Singh
ID: 17159804
its needed because the class Enum is also type-safe.
0

Featured Post

Tech or Treat!

Submit an article about your scariest tech experience—and the solution—and you’ll be automatically entered to win one of 4 fantastic tech gadgets.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

This was posted to the Netbeans forum a Feb, 2010 and I also sent it to Verisign. Who didn't help much in my struggles to get my application signed. ------------------------- Start The idea here is to target your cell phones with the correct…
In this post we will learn different types of Android Layout and some basics of an Android App.
Viewers learn about the scanner class in this video and are introduced to receiving user input for their programs. Additionally, objects, conditional statements, and loops are used to help reinforce the concepts. Introduce Scanner class: Importing…
Viewers will learn about if statements in Java and their use The if statement: The condition required to create an if statement: Variations of if statements: An example using if statements:
Suggested Courses

649 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question