通用阵列创建编译错误从内部类 [英] Generic Array Creation Compilation Error From Inner Class
问题描述
我想使用泛型，像下面这样来实现链接的集合。
I'm trying to implement a linked collection using generics, something like the following.
public class A<E> {
private class B {
private B[] b;
private E item;
private B() {
this.b = new B[2];
}
} // end inner class B
} // end class A
一个是引用接班人/ predecessors和项目使用数组集合中的集合和B的元素或节点。
A is the collection and B an element or node in the collection with an array referencing successors/predecessors and an item.
该阵列创建是不允许的。我得到的错误是通用阵列创建。我说得对认为它实际上是创建的数组A＆LT; E＆GT; .B ？
The array creation is not allowed. The error I get is generic array creation. Am I right to think that what it's actually creating is an array of A<E>.B?
如果没有，是什么造成的错误？
If not, what's causing the error?
如果是这样，我怎么能解决这个问题？
If so, how can I get around this?
我已经很明显忽略code一笔可观的，如果我所提供的是不够的，请让我知道。任何意见将是AP preciated。谢谢你。
I have obviously omitted a substantial amount of code, if what I've provided is not enough please let me know. Any advice would be appreciated. Thank you.
编辑1：我应该提到的是参数化类型必须在 A 等同于 B 。因此，通过＆LT; E＆GT; 的内部类是不可能的，因为它创建电子＃2 和叶 A 与电子＃1 。
EDIT 1: I should have mentioned that the parameterized type must be the same in A as in B. So passing <E> to the inner class is not possible, as it creates E#2 and leaves A with E#1.
推荐答案
您拨打 B 继承外部类的通用的，因为它不是一成不变的。而你不能只让静态的，因为它会再需要电子也。
You call B inherits the generic from the outer class, as it is not static. And you can't just make it static, because it will then need E also.
所以你的降B 阵列将确实需要一个类型，是通用的，即 A＆LT; E＆GT; .B 或如果您希望您的code更改为的静态的内部类， A·B＆LT; E＆GT; （如果你会使用私有静态类B＆LT; E＆GT; ）
So your B.b array will indeed need a type that is generic, i.e. A<E>.B or if you'd change your code to a static inner class, A.B<E> (if you would use private static class B<E>).
在Java中，由于泛型实施（通过擦除）的方式，在阵列的类型不明确的。一方面，它应该是 B ，在另一方面，它应该是一个数组的数组对象
In Java, due to the way generics are implemented (by erasure), the type of the array is not well-defined. On one hand, it should be an array of B, on the other hand, it should be an array of Object.
最可行的办法似乎是使用对象[] 和显式转换。
如果你想增加的类型安全，你当然可以使用的ArrayList＆LT; B＆GT; ，其内部使用对象[] 呢！
The most workable solution seems to be to use Object[] and cast explicitly.
If you want increased type safety, you can of course use an ArrayList<B>, which internally uses Object[], too!
在你特别code， B B1，B2; 也可能是一个选项，它实际上是快（没有边界检查），并需要更少的内存（没有数组反对;没有大小的信息）
In you particular code, B b1, b2; might also be an option which is actually faster (no bounds checking) and needs less memory (no array object; no size information).
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