从地图中删除多个按键有效吗？ [英] Remove multiple keys from Map in efficient way?

问题描述

我有一个 Map< String，String> 与大量的键值对。现在我想从 Map 中删除​​所选的键。以下代码显示了我做了什么。

I have a Map<String,String> with large number of key values pairs. Now I want to remove selected keys from that Map. Following code shows what I did to achieve that.

Set keySet = new HashSet(); //I added keys to keySet which I want to remove. 

然后：

Iterator entriesIterator = keySet.iterator();
while (entriesIterator.hasNext()) {
   map.remove( entriesIterator.next().toString());
} 

这是正常工作。我只是想知道，什么是更好的方式来达到我的要求？

This is working. I just want to know, what would be a better way to achieve my requirement ?

推荐答案

假设您的集合包含要删除的字符串，可以使用 keySet 方法和 map.keySet（）。removeAll（keySet）; 。

Assuming your set contains the strings you want to remove, you can use the keySet method and map.keySet().removeAll(keySet);.

keySet 返回此地图中包含的键的Set视图。该集合由地图支持，因此对地图的更改将反映在该集合中，反之亦然。

keySet returns a Set view of the keys contained in this map. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa.

适用的示例：

Map<String, String> map = new HashMap<>();
map.put("a", "");
map.put("b", "");
map.put("c", "");

Set<String> set = new HashSet<> ();
set.add("a");
set.add("b");

map.keySet().removeAll(set);

System.out.println(map); //only contains "c"

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