用它的泛型类型返回一个Class实例

问题描述

下面是一个简单的例子，演示了我正在运行的与类型擦除相关的问题。我有这样的一个类：

 是 Class 。我查看了，并且 getRawType 方法看起来很有前途，但它返回 Class< ;?超级T> 。
 
 
 
我暂时有一个解决方法，看起来像这样：
 
 
  public class ThingListMap {
 private Map< String，List< Thing>> thingListMap; 
 
 ... 
} 
  
我只是使用 ThingListMap 作为泛型类型参数。
 
 
 
另一个可能的解决方法是执行强制转换：
  public Class< Map< String，List< Thing>>>新的HashMap< String，List< Thing>>（）。getClass（）;返回类型的值。 
} 
  
有没有更优雅的方式来做到这一点？
 
 
 
 编辑：为回应其中一个答案，我无法更改 handledType 方法的签名我不拥有或控制它的源代码。
解决方案
由于某些原因，Java不允许您将 Map.class 直接到 Class< Map< String，List< Thing>>> 。这是一个未经检查的演员。 
 
 
但是将它投出两次是合法的，首先是 Class < / code>然后到 Class< Map< String，List< Thing>>>< / code>  
 
 
  return（Class   
作为未经检查的转换，您可能需要添加 @SuppressWarnings（unchecked ）。  
Here's a simple example that demonstrates a type-erasure-related issue I am running into. I have a class like this:
public abstract class AbstractHandler<T> {

    ...
    public abstract Class<T> handledType();
}
Then I have this implementation:
public class ConcreteHandler extends AbstractHandler<Map<String, List<Thing>>> {

    @Override
    public Class<Map<String, List<Thing>>> handledType() {
        //what do I return here?!
    }
}
I can't return Map<String, List<Thing>>.class, since that's not even valid syntactically. I tried making the generic type-parameter in the subtype to be HashMap<String, List<Thing>> and then returning new HashMap<String, List<Thing>>().getClass(), but that doesn't work because the return type of Class<T>#getClass() is Class<? extends T>. I looked at TypeToken from Guava, and the getRawType method seemed promising, but it returns Class<? super T>.
I have a workaround for the time being that looks like this:
public class ThingListMap {
    private Map<String, List<Thing>> thingListMap;

    ...
}
and I just use ThingListMap as the generic type-parameter.
Another possible workaround is to perform a forced cast:
public Class<Map<String, List<Thing>>> handledType() {
    return (Class<Map<String, List<Thing>>>) new HashMap<String, List<Thing>>().getClass();
}
Is there a more-elegant way to do this?
EDIT: In response to one of the answers, I cannot change the signature of the handledType method since I do not own or control its source.
 解决方案 
For some reason, Java doesn't allow you to cast Map.class directly to Class<Map<String, List<Thing>>>.  It's an unchecked cast anyway.
But it's legal to cast it twice, first to Class<?>, then to Class<Map<String, List<Thing>>>.
return (Class<Map<String, List<Thing>>>) (Class<?>) Map.class;
Being an unchecked cast, you may want to add @SuppressWarnings("unchecked"). 
                        
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