[英]Java 8 Convert HashSet to HashMap
I'm trying to convert hashset
to hashmap
in Java 8 using lambda and Collectors but I'm failing to do so. 我正在尝试使用lambda和Collectors将
hashset
转换为hashset
中的hashmap
,但我没有这样做。 Below is my code : 以下是我的代码:
Set<String> set = new HashSet<String>();
set.add("1");
set.add("2");
set.add("3");
HashMap<String, Integer> map = set.stream().collect(Collectors.toMap(x -> x, 0));
But the above is giving error as following: 但上面给出的错误如下:
The method toMap(Function<? super T,? extends K>, Function<? super T,? extends U>) in the type Collectors is not applicable for the arguments ((<no type> x) -> {}, int)
I'm a newbie in lambdas. 我是lambdas的新手。 Any help?
有帮助吗?
There are two issues: toMap()
returns a Map, not necessarily a HashMap, and the second argument needs to be a function. 有两个问题:
toMap()
返回一个Map,不一定是HashMap,第二个参数需要是一个函数。
For example: 例如:
Map<String, Integer> map = set.stream().collect(Collectors.toMap(x -> x, x -> 0));
final map map = set.stream()。collect(Collectors.toMap(Function.identity(),key - > 0));
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