java method returning an instance of Class<T extends Somethng>
generics, java, java-7
Solution
With a generic method like `getScrapper()`, the caller of the method determines what the actual type argument to the method is (`T` in this case). The caller could pick any subtype of `Scrapper` as `T`, and your method (which always returns `MyScrapper.class`) would not be returning the correct class.
Given the signature of the method, the caller of this method would expect to be able to do this:
Class<MyOtherScrapper> c = foo.<MyOtherScrapper>getScrapper();
Changing the method to return `Class<? extends Scrapper>` makes it no longer a generic method... there are no type parameters for the caller to set. Instead, the signature says that the method returns the class object for some unknown subtype of `Scrapper`, and `MyScrapper.class` does fit the bill for that.
Problem
i've got this code: ``` public <T extends Scrapper> Class<T> getScrapper() { return MyScrapper.class; } ``` `MyScrapper` is a class implementing `Scrapper` interface. Why is this not working? U'm getting the following error in JDK7: ``` error: incompatible types required: Class<T> found: Class<MyScrapper> where T is a type-variable: T extends Scrapper declared in method <T>getScrapper() ``` P.S. I've honestly tried searching for whole 30-40 minutes. Update: if i declare the method as `public Class<? extends Scrapper> getScrapper() {` it works. but I still don't understand why the original declaration was not compiling. what's wrong with it?