如何从HashMap中删除重复的值 [英] How to remove duplicate values from a HashMap

问题描述

我不知道如何最好地描述我的问题，但在这里，我试图从 HashMap< String，String>中删除相同的名称（值）例如，如果此映射包含像


这样的名称，则map = new HashMap< String，String>（）;

  map.put（Vivaldi，Antonio）; 
 map.put（Belucci，Monica）; 
 map.put（Gudini，Harry）; 
 map.put（Verdo，Dhuzeppe）; 
 map.put（Maracci，Bruno）; 
 map.put（Carleone，Vito）; 
 map.put（Bracco，Luka）; 
 map.put（Stradivari，Antonio）; 
  

我想通过使用方法<$ c $删除所有具有值Antonio的条目c> removeTheFirstNameDuplicates ，我在Google上查了几天，所有的例子都接近我想要的，但不是真正需要的。

我的想法是，我需要检查地图的东西，如果它包含相同的值，则删除重复。但我该怎么做呢？

解决方案

你可以用下面的方法来完成它： p>

  private static void removeTheFirstNameDuplicates（final Map< String，String> map）{
 final Iterator< Entry< String，String> > iter = map.entrySet（）。iterator（）; 
 final HashSet< String> valueSet = new HashSet< String>（）; 
 while（iter.hasNext（））{
 final Entry< String，String> next = iter.next（）; 
 if（！valueSet.add（next.getValue（）））{
 iter.remove（）; 
 
 
 
 code $ 
 $ 添加（）方法 HashSet 将返回 false 如果已添加一个值到集合。上面的方法使用它来检测已找到重复项，然后使用 remove（） HashMap 中删除​​重复项
 
 
值得注意的是，根据你使用的 Map 实现，如果你使用 TreeMap 而不是 HashMap ，您肯定会按键字母顺序遍历地图Berluccio，Bracco，Carleone ... Verdo。然后，你会始终保持Stradivari并删除Vivaldi。
 
I don't know how can best describe my problem but here it is, I'm trying to remove the same names(values) from HashMap<String, String> map = new HashMap<String, String>();

for example if this map contain names like 
    map.put("Vivaldi","Antonio");
    map.put("Belucci", "Monica");
    map.put("Gudini", "Harry");
    map.put("Verdo", "Dhuzeppe");
    map.put("Maracci", "Bruno");
    map.put("Carleone", "Vito");
    map.put("Bracco", "Luka");
    map.put("Stradivari", "Antonio");
I want to remove all entries with the value "Antonio" from it by using method removeTheFirstNameDuplicates, I looked in Google for a couple of days and all examples are close to what I want but not really what I need.

My thoughts are, I need something that will check a map and if it contains the same values in it then remove the duplicate. But how can I do this?
解决方案
You can do it with the following method which only iterates over the map once:
private static void removeTheFirstNameDuplicates(final Map<String, String> map) {
    final Iterator<Entry<String, String>> iter = map.entrySet().iterator();
    final HashSet<String> valueSet = new HashSet<String>();
    while (iter.hasNext()) {
        final Entry<String, String> next = iter.next();
        if (!valueSet.add(next.getValue())) {
            iter.remove();
        }
    }
}
The add() method on HashSet will return false if a value has already been added to the set. The method above uses this to detect that a duplicate has been found and then removes the duplicate from the HashMap by using the remove() method on the iterator.

It is worth noting that, depending on the Map implementation you use, the iteration order may not be guaranteed so which duplicate you remove is also not guaranteed.

If you were to use a TreeMap rather than a HashMap you would be certain to iterate over the map alphabetically by key e.g. Berluccio, Bracco, Carleone … Verdo. You would then always keep Stradivari and remove Vivaldi.

                        
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