What does > mean in Java?

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感动是毒
感动是毒 2021-02-10 09:44

I\'m creating an interface of JOOQ TableRecord

> 

Would anyone be able to explain the line above?

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  • 2021-02-10 10:25

    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(...);
    
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  • 2021-02-10 10:45
    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

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