我可以将泛型属性存储到对象的字段中 [英] Can I store the generics attribute into an object's field

问题描述

假设以下类存根：

  public class Foo< T> {
私人课程< T>类型; 
 
 public Foo< T> （）{} 
} 
  

我可以存储泛型类型 T 在构造函数中的类型字段中，而不改变构造函数的签名为 public Foo< T>（Class< T>类型）？



如果是，如何？如果不是，为什么？

type = T 似乎不起作用。

$无类型擦除意味着您必须在执行时提供 。 您可以提供 T 或 Class 的实例，但类本身只会出现T替换为 Object 。

这种事情是Java泛型与.NET中最大的缺点之一。 （另一方面，差异的故事更强 - 如果更容易混淆 - 在Java中比在.NET中）。

Assuming the following class stub:

public class Foo<T> {
  private Class<T> type;

  public Foo<T> () {}
}

Can I store the generic type T into the field type in the constructor, without changing the constructor's signature to "public Foo<T> (Class<T> type)"?

If yes, how? If no, why?

"type = T" doesn't seem to work.

解决方案

No - type erasure means that you have to provide something at execution time. You could provide either an instance of T or Class<T> but the class itself will just have every occurrence of T replaced with Object.

This kind of thing is one of the biggest disadvantages of Java's generics vs those in .NET. (On the other hand, the variance story is stronger - if more confusing - in Java than in .NET.)

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