为什么不能为泛型自动填充Java基本类型？ [英] Why not auto-box Java primitive types for Generics?

问题描述

Java不允许在通用数据结构中使用基本类型。例如。的ArrayList< INT>不允许。原因是，原始类型不能直接转换为Object。但是，Java 1.5确实支持自动装箱，并且包装类在普通数据结构中工作。那么为什么编译器不能将它自动装箱到ArrayList< Integer>？是否还有其他原因导致这种情况无法正常工作？

解决方案

据我了解，您提出的 ArrayList< int> 将与 ArrayList< Integer> 相同。是对的吗？ （换句话说，在内部它仍然存储一个Integer;每次你把东西放进去或者把它拿出来，它会自动地对它进行box / unbox，但是autoboxing / autounboxing已经为 ArrayList< Integer> ）





如果它是相同的，那么我不明白具有重复语法< int> 表示与< Integer> 相同的内容。 （实际上它会引入额外的问题，因为例如 int [] 与 Integer [] ，所以如果你有 T [] ，并且 T 是 int ，这是什么意思？）

Java does not allow primitive types to be used in generic data structures. E.g. ArrayList<int> is not allowed. The reason is, primitive types can not be directly converted to Object. However Java 1.5 does support auto-boxing, and wrapper classes work in generic data structures. So why couldn't the compiler auto-box it to ArrayList<Integer>? Are there any other reasons for why this can not work?

解决方案

So as far as I understand it, your proposed ArrayList<int> would be identical to ArrayList<Integer>. Is that right? (In other words, internally it still stores an Integer; and every time you put something in or get it out, it would automatically box/unbox it, but autoboxing/autounboxing already does that for ArrayList<Integer>.)

If it is the same, then I don't understand what is the utility of having a duplicate syntax <int> that means the same thing as <Integer>. (In fact it will introduce additional problems, because for example int[] is not the same runtime type as Integer[], so if you have T[], and T is int, what would it mean?)

这篇关于为什么不能为泛型自动填充Java基本类型？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！