我们可以代表“自类"吗?在Java(或Kotlin)中? [英] Can we represent "self class" in Java (or Kotlin)?

问题描述

我认为问题标题有点令人困惑，但是我找不到更准确的说法.
我只需要一个简单的代码示例即可告诉您我想要什么.

I think the question title is a little bit confusing, but I can't find a more precise way to say this.
I just need a simple code example to tell you what I want.

我有:

// code 1
interface A { A bla(); }
class B implements A { @Override public B bla() { return this; } }
class C implements A { @Override public C bla() { return this; } }

但是实际上，该代码也将编译(差异:查看返回类型声明):

But actually, this code will compile too (diff: look at the return type declaration):

// code 2
interface A { A bla(); }
class B implements A { @Override public A bla() { return this; } }
class C implements A { @Override public A bla() { return this; } }

我希望代码2是类型错误.
说，我想强制每个A的子类的bla方法返回其自身，而不是A.

I want code 2 to be a type error.
Say, I want to force every A's subclass' bla method to return their self, instead of an A.

我认为可能存在伪造的代码来表示我想要的东西:

I think there can be a fake code to represent what I want:

interface A { this.Type bla(); }

就像Haskell的类型类一样:

Just like Haskell's typeclasses:

class Monad (m :: * -> *) where
  -- here m is restricted to the subclass
  (>>=) :: m a -> (a -> m b) -> m b

这可能吗?

推荐答案

不可能，但是你可以做到

Not possible, but you can do that

interface A<T extends A> { T bla();}
class B implements A<B> { @Override public B bla() { return this; } }
class C implements A<C> { @Override public C bla() { return this; } }

这篇关于我们可以代表“自类"吗?在Java(或Kotlin)中?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！