What does <?> stand for in Java? [duplicate]

Question

Possible Duplicate:
Java Generics

In Eclipse, I am given warnings for using 'rawtypes' and one of it's fixes is to add <?>. For example:

    Class parameter = String.class;
    //Eclipse would suggest a fix by converting to the following:
    Class<?> parameter = String.class;

What does this <?> actually mean?

Answer 1

Class<?> should be interpreted as a Class of something, but the something isn't known or cared about.

It's the use of Java generic types. Class in Java 5 or greater is a parameterized type, so the compiler expects a type parameter. Class<String> would work in the specific context of your code, but again, in many cases you don't care about the actual type parameter, so you can just use Class<?> which is telling the compiler that you know Class expects a type parameter, but you don't care what the parameter is.

Answer 2

Raw types refer to using a generic type without specifying a type parameter. For example, List is a raw type, while List<String> is a parameterized type

See this document for more info: http://www.javapractices.com/topic/TopicAction.do?Id=224