Java 8中致命的死亡钻石 [英] Deadly Diamond of Death in Java 8

问题描述

我是一名Java开发人员，我一直在学习C ++。我最近在C ++中进入了致命的死亡钻石，并研究了这个问题是否可能在Java中出现。在界面是否解决了致命的死亡之钻问题？，我发现了这个：

I'm a Java developer and I've been learning C++ on the side. I recently got into the "deadly diamond of death" in C++ and researched if this problem was possible in Java. In Do interfaces solve the "deadly diamond of death" issue?, I found this:

Java 8为方法搞砸了;现在，接口可以声明
默认方法和静态方法实现。这会带来一大块
的钻石死亡问题。

Java 8 screws this up for methods; an interface now can declare both default methods and static method implementations. This brings a large chunk of the Diamond of Death problem into the language.

我想知道是否会有人能够扩展Java 8为DDD引入的问题。

I'm wondering if someone would be able to expand on the problems introduced by Java 8 for the DDD.

推荐答案

我想引用的答案指的是Java中的这种情况： ¹

I imagine the quoted answer is referring to scenarios such as this in Java:¹

interface B {
    default void x() { System.out.println("B::x"); }
}

interface C {
    default void x() { System.out.println("C::x"); }
}

class D implements B, C {}

什么会像新的D（）。x（）在这里做什么？

What would something like new D().x() do here?

幸运的是，编译器禁止完全定义 D ，并带有以下消息：

Luckily, the compiler forbids the definition of D entirely, with the following message:

D inherits unrelated defaults for x() from types B and C

可以解决歧义（并满足编译器）通过在 D 中覆盖 x 。然后可以显式调用各个继承的默认方法：

One can resolve the ambiguity (and satisfy the compiler) by overriding x in D. One may then explicitly invoke the individual inherited default methods:

class D implements B, C {
    @Override
    public void x() {
        B.super.x();       // Note explicit interface names
        C.super.x();
    }
}

---

<子> 1。显然，这里没有钻石。但这是一个更简单的案例。我们可以添加接口A {void x（）; } 同时 B 和 C 扩展，但这不会改变结果。

---

_{1. Clearly, there's no diamond here. But this is an even simpler case. We could add interface A { void x(); } that both B and C extend, but that wouldn't change the result.}

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