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

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

Well you collect all the elements to a Map, where the key is the value itself, and value is how many times it is repeated. Later we stream the entry set from that resulting map and filter only those entries that that have a count of 1 (meaning they are not repeated), later we map to Entry::getKey - to get that value from the List and count.