用Java中的抽象类扩展抽象泛型类

Question

I have a base abstract class public abstract class BaseModel <T extends BaseModel<T>> . Normally, I extend this class with something like public class OtherModel extends BaseModel<OtherModel> . For some of my classes, I want to have an intermediate abstract class, such that A extends B extends BaseModel.

I'd like to be able to declare public class EndModel extends MiddleModel<EndModel> . The only way I've managed to get Eclipse to be happy is if I declare MiddleModel as public abstract class MiddleModel<T extends BaseModel<T>> extends BaseModel<T> , but this seems ugly, and now I have to add a type anywhere I declare a variable as MiddleModel , even if I don't actually care what type it is. Is there a better way to do this?

Answer 1

If you want to add more functionality in MiddleModel , which depends on the generic type of it, declare it like this:

public abstract class BaseModel <T extends BaseModel<T>> {}

public abstract class MiddleModel <T extends MiddleModel<T>> extends BaseModel<T> {}

public class EndModel extends MiddleModel<EndModel> {}

Note that EndModel doesn't support that extensibility. It's a trade-off, because I don't want to write new EndModel<EndModel>() but rather new EndModel() .