Re: Help. Generics notation really <P> me off

Lew <>
Thu, 15 Nov 2007 21:04:23 -0500
Jacob Singer wrote:

You're right db.query(Shape) does not work but db.query(Shape.class)
is good to go because query() is expecting a class type. So what I
need is the generics equivalent of Shape.class and I thought that
would be `T' but it is not so.

Please do not top-post.

As Joshua explained, T is not a variable. Shape.class is a variable. T is
like 'Shape' in the expression, as Joshua said, not 'Shape.class'.

You need the equivalent of T.class, except for you can't use that so you have
to pass in a Class<? extends T> somehow, just as Joshua said.

public class ObjectContainer ...

Ellipses don't compile, and "Object" is not a good class-name part.

Another approach is to make the Container class generic, too.

  public class Container<T extends Shape>
    public static MySet <T> query()

// Notice how the keyword "Class" is spelled with an upper-case 'C'.

      return null;

<!-- -->

  public class MyUsefulName <T extends Shape>
    private final Container<T> container = initContainer();
    public void exec()
      MySet <T> stuff = container.query();
      doMoreWith( stuff );

I didn't try to compile this, but it's a start for sure.


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