问题
I'm creating an interface of JOOQ TableRecord
<R extends TableRecord<R>>
Would anyone be able to explain the line above?
Thanks
回答1:
It means a class of type R, that implements the interface TableRecord<R>
TableRecord<R> means that the interface is bound to the same type R.
An example would be a class like:
public class Bla implements TableRecord<Bla>
I admit this seems a bit strange, but Java generics don't really differentiate between extends and implements, which leads to some confusion.
As to why this exact definition, I don't know enough about the context to see exactly why it makes sense, but it might be due to method signatures on the interface returning objects of type R (think Factory):
public R createTableRecord(...);
回答2:
class SomeClass<R extends TableRecord<R>>
What it means that parameter type R has to be a subclass of TableRecord <R> and nothing else, i.e. you must use class
class Foo extends TableRecord <Foo>
as the parameter for defining your class SomeClass
来源：https://stackoverflow.com/questions/18892061/what-does-r-extends-tablerecordr-mean-in-java