为什么Java自动装箱不会扩展到自动装箱类型方法的方法调用？ [英] Why doesn't Java autoboxing extend to method invocations of methods of the autoboxed types?

问题描述

我想将原语转换为字符串，我尝试了：

I want to convert a primitive to a string, and I tried:

myInt.toString();

此操作失败并显示错误：

This fails with the error:

int cannot be dereferenced

现在，我得到的原语不是引用类型（即不是Object）因此不能有方法。然而，Java 5引入了自动装箱和拆箱（一个C＃......我在C＃中从未喜欢过，但这不是重点）。因此，使用自动装箱，我希望上面的内容将myInt转换为Integer，然后调用toString（）。

Now, I get that primitives are not reference types (ie, not an Object) and so cannot have methods. However, Java 5 introduced autoboxing and unboxing (a la C#... which I never liked in C#, but that's beside the point). So with autoboxing, I would expect the above to convert myInt to an Integer and then call toString() on that.

此外，我相信C＃允许这样的调用，除非我记错了。这只是Java自动装箱/拆箱规范的一个不幸的缺点，还是有充分的理由呢？

Furthermore, I believe C# allows such a call, unless I remember incorrectly. Is this just an unfortunate shortcoming of Java's autoboxing/unboxing specification, or is there a good reason for this?

推荐答案

Java autoboxing /拆箱不会允许您取消引用基元，因此编译器会阻止它。您的编译器仍然知道 myInt 作为基元。在 jcp.org 上有一篇关于此问题的论文。

Java autoboxing/unboxing doesn't go to the extent to allow you to dereference a primitive, so your compiler prevents it. Your compiler still knows myInt as a primitive. There's a paper about this issue at jcp.org.

在分配或参数传递期间，自动装箱主要是有用的 - 允许您将基元作为对象传递（反之亦然），或者将基元分配给对象（反之亦然）。

Autoboxing is mainly useful during assignment or parameter passing -- allowing you to pass a primitive as an object (or vice versa), or assign a primitive to an object (or vice versa).

所以不幸的是，你必须这样做:(荣誉帕特里克，我改用你的方式）

So unfortunately, you would have to do it like this: (kudos Patrick, I switched to your way)

Integer.toString(myInt);

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