Java：将 HashMap 值转换为 Set<Integer>
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Java: convert HashMap values to Set<Integer>
提问by TonyGW
One more question about HashMap<> in Java:
关于 Java 中 HashMap<> 的另一个问题：
I have the following
我有以下
Map<String, Set<Integer>> myWordDict = new HashMap<String, Set<Integer>>();
After storing data into the variable myWordDict, I want to iterate through the HashMapValues, and add each value to a new Set variable?
将数据存储到变量后myWordDict，我想遍历 HashMapValues，并将每个值添加到新的 Set 变量中？
When I try to do Set<Integer> newVariable = myWordDict.entrySet(), it seems the data type is incompatible.
当我尝试这样做时Set<Integer> newVariable = myWordDict.entrySet()，数据类型似乎不兼容。
So my question is essentially:
所以我的问题本质上是：
how to convert HashMap values or entrySet() to Set ?
如何将 HashMap 值或 entrySet() 转换为 Set ？
Thanks
谢谢
采纳答案by Masudul
Your declaration should be like below. It will convert your map values to Collection
您的声明应如下所示。它会将您的地图值转换为Collection
Collection<Set<Integer>> newVariable = myWordDict.values();
回答by ApproachingDarknessFish
use myWordDict.values(), not myWordDict.entrySet(). values is a set of the map's values, whereas entrySetis a set of its mappings (it is a set of java.util.map.Entry objects, each of which describes a key and a value).
使用myWordDict.values()，不是myWordDict.entrySet()。values 是一组映射values，而entrySet是一组映射（它是一组 java.util.map.Entry 对象，每个对象描述一个键和一个值）。
回答by SudoRahul
If you need all the values as a Setof Integersand not as a Setof Set, then you could do something like this
如果您需要将所有值作为 a SetofIntegers而不是 a Setof Set，那么您可以执行以下操作
Set<Integer> newVariable = new HashSet<Integer>();
for (Set<Integer> set : myWordDict.values()) {
newVariable.addAll(set);
}
Or if you want them as a Setof Set, you need to do something like this
或者如果你想要它们作为Setof Set，你需要做这样的事情
Set<Set<Integer>> newVariable = new HashSet<Set<Integer>>();
newVariable.addAll(myWordDict.values());
回答by Rakesh KR
Map<Integer,String> map1 = new HashMap<Integer,String>();
map1.put(1, "Rakesh");
map1.put(2, "Amal");
map1.put(3, "Nithish");
Set<Entry<Integer,String>> set1 = map1.entrySet();
回答by Aniket Kulkarni
public Set<Map.Entry<K,V>> entrySet()
Returns a Set view of the mappings contained in this map. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa.
返回此映射中包含的映射的 Set 视图。该集合由地图支持，因此对地图的更改会反映在该集合中，反之亦然。
If you want iterate over the myWordDicthash map then just
如果您想遍历myWordDict哈希映射，那么只需
for(Map.Entry<String, Set<Integer>> entry : myWordDict.entrySet())
{
Set<Integer> newVariable = entry.getValue();
}
Related links
相关链接
回答by Kamlesh Arya
Try:
尝试：
Set<Integer> newVariable = mywordDict.keySet();
or
或者
Set<Integer> newVariable = new HashSet<Integer>(myWordDict.values());
回答by aga
回答by TonyGW
So, I came up with an iterator to iterate through the value Set
所以，我想出了一个迭代器来迭代值 Set
I have this data structure
我有这个数据结构
Map<String, Set<Integer>> myWordDict = new HashMap<String, Set<Integer>>();
I created
我创建
Iterator mapIterator = myWordDict.entrySet().iterator();
Then just use a while() loop to add individual value to a new Set variable. I am not sure this is the most efficient way, but it works for my needs.`
然后只需使用 while() 循环将单个值添加到新的 Set 变量中。我不确定这是最有效的方法，但它适合我的需要。`
回答by freeն
flatMap will help you:
flatMap 将帮助您：
myWordDict.values().stream().flatMap(Set::stream).collect(Collectors.toSet());
