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0 pointsblasdel16y ago0 comments

But can you pass classes around as objects after they're loaded? Do they have a value beyond their identifier?

0 comments

pvg16y ago

Yep, you can pass them around, they do have values, in fact, they can have different values for the same type sometimes. This has been the case since well before Java even had reflection - having them around is fairly central to the Java dynamic loading and security model.

dminor16y ago

Yes, although Java's reflection is somewhat of a pain in the ass and limited in many ways. But you can take a Class object and call newInstance(), and it will invoke the class's no-arg constructor.

duskwuff16y ago

Moreover, reflection is less of a language feature and more of a very low-level library feature. In ObjC, one can write

    Class c = [SomeRandomClass class];
    id thingy = [[c alloc] init];

but Java won't let you do the equivalent:

    Class c = SomeRandomClass;
    Object x = new c;

vlisivka16y ago

  Class c = SomeRandomClass.class;
  Object x=c.newInstance();

1 more reply

lucifer16y ago

When you define a class, say "Foo", instances of Foo are Foo objects. "Foo", itself, is an instance of a class named "Class" which is a direct descendent of the class "Object".

In Java's type system, classes are 'first class objects':

http://en.wikipedia.org/wiki/First-class_object

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