是否有收集到订单保留集的收集器？ [英] Is there a Collector that collects to an order-preserving Set?

问题描述

Collectors.toSet（）不保留顺序。我可以使用Lists代替，但我想表明结果集合不允许元素重复，这正是 Set 接口的用途。

Collectors.toSet() does not preserve order. I could use Lists instead, but I want to indicate that the resulting collection does not allow element duplication, which is exactly what Set interface is for.

推荐答案

您可以使用 toCollection 并提供所需集合的具体实例。例如，如果您想保留广告订单：

You can use toCollection and provide the concrete instance of the set you want. For example if you want to keep insertion order:

Set<MyClass> set = myStream.collect(Collectors.toCollection(LinkedHashSet::new));

例如：

public class Test {    
    public static final void main(String[] args) {
        List<String> list = Arrays.asList("b", "c", "a");

        Set<String> linkedSet = 
            list.stream().collect(Collectors.toCollection(LinkedHashSet::new));

        Set<String> collectorToSet = 
            list.stream().collect(Collectors.toSet());

        System.out.println(linkedSet); //[b, c, a]
        System.out.println(collectorToSet); //[a, b, c]
    }
}

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