什么< R扩展TableRecord< R>>用Java表示？ [英] What does <R extends TableRecord<R>> mean in Java?

问题描述

我正在创建一个JOOQ的界面 TableRecord

I'm creating an interface of JOOQ TableRecord

<R extends TableRecord<R>> 

有人能够解释上述行吗？

Would anyone be able to explain the line above?

谢谢

推荐答案

这意味着一个类型为R的类，它实现了接口 TableRecord< R>

It means a class of type R, that implements the interface TableRecord<R>

TableRecord< R> 表示接口绑定到该接口类型R。

TableRecord<R> means that the interface is bound to the same type R.

一个例子是类：

public class Bla implements TableRecord<Bla>

我承认这看起来有点奇怪，但Java泛型并没有真正区分 extends 和 implements ，这会导致一些混乱。

I admit this seems a bit strange, but Java generics don't really differentiate between extends and implements, which leads to some confusion.

至于为什么这个确切的定义，我不太了解上下文，看看它究竟为什么有意义，但它可能是由于接口上的方法签名返回 R 类型的对象（想想工厂）：

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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