Java泛型中有联盟吗？ [英] Is there a Union in Java Generics?

问题描述

我可以在集合中包含两种不同的类型吗？例如，我可以有List< String U Integer>？

解决方案

简短的回答？不，你可以（当然）有一个 List 对象，但你可以把 / em>，而不仅仅是 String 或 Integer 对象。

您可以创建一个容器对象列表，该容器对象将包含整数或 String （也许通过泛型）。更麻烦一点。

  public class Contained< T> {
 T getContained（）; 
} 
  

并实现 Contained< Integer> 和包含< String> 。

当然，真正的问题是你为什么要这样做？我期望一个集合包含相同类型的对象，然后我可以迭代并对这些对象执行操作，而不用担心它们是什么。也许你的对象层次需要进一步思考？

Can I contain two different types in a collection? For example, can I have List< String U Integer > ?

解决方案

Short answer ? No. You can (of course) have a List of Objects, but then you can put anything in it, not just String or Integer objects.

You could create a list of container objects, and that container object would contain either an Integer or String (perhaps via generics). A little more hassle.

public class Contained<T> {
   T getContained();
}

and implement Contained<Integer> and Contained<String>.

Of course, the real question is why you want to do this ? I would expect a collection to contain objects of the same type, and then I can iterate through and perform actions on these objects without worrying what they are. Perhaps your object hierarchy needs further thought ?

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