类型安全,通用,空集合与静态泛型 [英] Type-safe, generic, empty Collections with static generics
问题描述
我尽可能返回空集合与null。我可以使用 java在两种方法之间切换.util.Collections :
I return empty collections vs. null whenever possible. I switch between two methods for doing so using java.util.Collections:
return Collections.EMPTY_LIST;
return Collections.emptyList();
其中 emptyList()
类型安全。但我最近发现:
where emptyList()
is supposed to be type-safe. But I recently discovered:
return Collections.<ComplexObject> emptyList();
return Collections.<ComplexObject> singletonList(new ComplexObject());
等。
在Eclipse包资源管理器中:
I see this method in Eclipse Package Explorer:
<clinit> () : void
但我不知道如何在源代码。
but I don't see how this is done in the source code (1.5). How is this magic tomfoolerie happening!!
编辑:
如何实现静态泛型类型? $ b
推荐答案
编辑:如何实现静态泛型类型
?
How is the static Generic type accomplished?
http ://www.docjar.com/html/api/java/util/Collections.java.html
public class Collections {
...
public static final List EMPTY_LIST = new EmptyList<Object>();
...
public static final <T> List<T> emptyList() {
return (List<T>) EMPTY_LIST;
}
...
}
链接来实现EmptyList类,如果你好奇,但对你的问题,这没关系。
You can see the link for the implementation of the EmptyList class if you're curious, but for your question, it doesn't matter.
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