Java 8 流 : get non repeated counts

Question

这是输入和输出的 SQL 版本:

     with tab1 as (

        select 1 as id from dual union all
        select 1 as id from dual union all
        select 2 as id from dual union all
        select 2 as id from dual union all
        select 5 as id from dual 
        )

    select id from tab1 group by id having count(id)=1;

Output is Id=5 and count is 1

因为 5 是非重复的。我如何使用 JAVA 8 流实现它？

我在下面尝试过，但显然它给出了错误的结果

List<Integer> myList = new ArrayList<Integer>();
                myList.add(1);
                myList.add(1);
                myList.add(2);
                myList.add(2);
                myList.add(5);

                Long f =  myList.stream()
                          .distinct().count();

                System.out.println(f);

Answer 1

long result = myList.stream()
         .collect(Collectors.groupingBy(
                   Function.identity(),
                  Collectors.counting()))
         .entrySet()
         .stream()
         .filter(entry -> entry.getValue() == 1)
         .map(Entry::getKey)
         .count();

好吧，您将所有元素收集到 Map<Integer, Long> ，其中键是值本身，值是重复的次数。稍后我们从生成的 map 和 filter 流式传输条目集。只有那些计数为 1 的条目(意思是它们不重复)，稍后我们 map至 Entry::getKey - 从列表中获取该值并计数。