如何访问Java中的嵌套HashMaps？ [英] How do I access nested HashMaps in Java?

问题描述

我在Java中有一个HashMap，它的内容（你可能都知道）可以被访问

I have a HashMap in Java, the contents of which (as you all probably know) can be accessed by

HashMap.get("keyname");

如果在另一个HashMap中有一个HashMap，也就是一个嵌套的HashMap，我将如何访问这些内容？我可以这样做，内联：

If a have a HashMap inside another HashMap i.e. a nested HashMap, how would i access the contents? Can i do this like this, inline:

HashMap.get("keyname").get("nestedkeyname");

谢谢。

Thank you.

推荐答案

你可以像你想的那样去做。但是你的HashMap必须被模板化：

You can do it like you assumed. But your HashMap has to be templated:

Map<String, Map<String, String>> map = 
    new HashMap<String, Map<String, String>>();

否则，您必须转换为 Map 从第一个地图中检索第二个地图。

Otherwise you have to do a cast to Map after you retrieve the second map from the first.

Map map = new HashMap();
((Map)map.get( "keyname" )).get( "nestedkeyname" );

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