Java 泛型类 - 确定类型 [英] Java Generic Class - Determine Type

问题描述

如果我要创建一个泛型的java类，例如:

If I am creating a java class to be generic, such as:

public class Foo<T>

如何在内部确定该类的T"最终是什么?

How can one determine internally to that class, what 'T' ended up being?

public ???? Bar()
{
    //if its type 1
    //    do this
    //if its type 2
    //    do this
    //if its type 3
    //    do this
    //if its type 4
    //    do this
}

我已经研究了 Java API 并使用了 Reflection 的东西、instanceof、getClass、.class 等，但我似乎无法对它们做出正面或反面.我觉得我很接近了，只需要结合一些电话，但要保持简短.

I've poked around the Java API and played with the Reflection stuff, instanceof, getClass, .class, etc, but I can't seem to make heads or tails of them. I feel like I'm close and just need to combine a number of calls, but keep coming up short.

更具体地说，我试图确定该类是否使用 3 种可能类型之一进行了实例化.

To be more specific, I am attempting to determine whether the class was instantiated with one of 3 possible types.

推荐答案

我在一些项目中使用了与他在此处解释的解决方案类似的解决方案，发现它非常有用.

I've used a similar solution to what he explains here for a few projects and found it pretty useful.

http://blog.xebia.com/2009/02/07/accessing-generic-types-at-runtime-in-java/

它的要点是使用以下内容:

The jist of it is using the following:

 public Class returnedClass() {
     ParameterizedType parameterizedType = (ParameterizedType)getClass()
                                                 .getGenericSuperclass();
     return (Class) parameterizedType.getActualTypeArguments()[0];
}

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