Java 8 Streams : get non repeated counts

Question

Here is the SQL version for the input and output :

     with tab1 as (

        select 1 as id from dual union all
        select 1 as id from dual union all         


        

Answer 1

Another option for you to consider:

    //Create a map where the key is the element you want to count and the value is the actual count
    Map countByItem = myList.stream()
        .collect(Collectors.groupingBy(
                Function.identity(), //the function that will return the key
                Collectors.counting())); //the function that will actually count the occurences

    //Once you have that map, all you need to do is filter for the registers with count == 1
    List result = countByItem.entrySet().stream()
        .filter(entry -> entry.getValue() == 1)
        .map(Map.Entry::getKey)
        .collect(Collectors.toList());