遍历嵌套的 hashmap [英] Iterate through nested hashmap

问题描述

我将如何遍历嵌套的 HashMap?

How would I go about iterating through a nested HashMap?

HashMap 设置如下:

HashMap<String, HashMap<String, Student>>

其中Student 是一个包含变量name 的对象.例如，如果我的 HashMap 看起来像这样(以下不是我的代码，只是为了模拟 hashmap 的内容可能是什么)

Where Student is an object containing a variable name. If for instance my HashMap looked like this (the following is not my code, it's just to simulate what the contents of the hashmap could be)

 hm => HashMap<'S', Hashmap<'Sam', SamStudent>>
       HashMap<'S', Hashmap<'Seb', SebStudent>>
       HashMap<'T', Hashmap<'Thomas', ThomasStudent>>

我怎样才能遍历所有的单字母键，然后是每个全名键，然后提取学生的姓名?

How could I iterate through all of the single letter keys, then each full name key, then pull out the name of the student?

推荐答案

for (Map.Entry<String, HashMap<String, Student>> letterEntry : students.entrySet()) {
    String letter = letterEntry.getKey();
    // ...
    for (Map.Entry<String, Student> nameEntry : letterEntry.getValue().entrySet()) {
        String name = nameEntry.getKey();
        Student student = nameEntry.getValue();
        // ...
    }
}

...和 ​​Java 10 中的 var 关键字可以消除泛型冗长:

...and the var keyword in Java 10 can remove the generics verbosity:

for (var letterEntry : students.entrySet()) {
    String letter = letterEntry.getKey();
    // ...
    for (var nameEntry : letterEntry.getValue().entrySet()) {
        String name = nameEntry.getKey();
        Student student = nameEntry.getValue();
        // ...
    }
}

这篇关于遍历嵌套的 hashmap的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！