使用反射在Java中创建通用参数化类 [英] Use reflection to create a generic parameterized class in Java

问题描述

如何使用反射在Java中创建泛型参数化类？

我有

  public class SomeClass< T> {
 public SomeClass< T>（）{
} 
} 
  

<

我尝试了

  Class c = Class.forName（SomeClass）; 
  

但是找不到一个语法来让我得到一个适当类型的实例，比如

  SomeType instance =（SomeType）Class.forName（SomeClass< SomeType>）。createInstance（）; 
  

所以，我怎么能这样做？

List< Integer> 和 List< String> 在运行时被视为相同类型）。因为反射本质上是一个运行时功能，所以类型参数根本不被使用或涉及。

换句话说，你只能实例化原始类型（ SomeClass ，而不是 SomeClass< T> ）。然后您必须手动将该类型转换为通用版本（并生成未经检查的警告）。

How can I use reflection to create a generic parameterized class in Java?

I have

public class SomeClass<T> {
   public SomeClass<T>() {
   }
}

and I need an instance of it.

I've tried variations of

Class c = Class.forName("SomeClass");

but could not find a syntax that would allow me to get an appropriately typed instance, like, say

SomeType instance = (SomeType)Class.forName("SomeClass<SomeType>").createInstance();

So, how could I go about doing this?

解决方案

Java uses erasure-based generics (i.e., the type parameters are erased at runtime—for example, List<Integer> and List<String> are treated as the same type at runtime). Since reflection is inherently a runtime feature, the type parameters are not used or involved at all.

In other words, you can only instantiate the raw type (SomeClass, not SomeClass<T>) when you're using reflection. You will then have to manually cast the type to the generic version (and generate an unchecked warning).

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