如何在哈希图中打印具有重复值的键? [英] How to print keys with duplicate values in a hashmap?

问题描述

我有一个哈希映射，其中一些键指向相同的值.我想找到所有相等的值并打印相应的键.

I have a hashmap with some keys pointing to same values. I want to find all the values that are equal and print the corresponding keys.

这是我当前拥有的代码:

This is the current code that I have:

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

    map.put("hello", "0123");
    map.put("hola", "0123");
    map.put("kosta", "0123");
    map.put("da", "03");
    map.put("notda", "013");

    map.put("twins2", "01");
    map.put("twins22", "01");


    List<String> myList = new ArrayList<>();

    for (Map.Entry<String, String> entry : map.entrySet()) {
       for (Map.Entry<String, String> entry2 : map.entrySet()){
           if (entry.getValue().equals(entry2.getValue()))
           {
               myList.add(entry.getKey());
           }
       }

    }

当前代码将重复项两次添加到列表中，但是也会将每个键一次添加一次.

The current code adds the duplicates two times into the list, however it also adds every key one time.

谢谢.

推荐答案

您可以使用流以这种方式检索重复项:

You can use streams to retrive duplicates in this way:

  List<String> myList = map.stream()
     .filter(n -> Collections.frequency(map.values(), n) > 1)
     .collect(Collectors.toList());

然后，您可以使用以下命令将其打印出来:

And then, you can print this out with:

myList.foreach(System.out::println);

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