In java streams is it possible to use the variable that you will get on a filter clause inside the scope of a map?

Question

I'm trying to reproduce the following behavior with the help of streams:

public List<ObjDTO> getList(param1){
        List<SomeObj> allObjs = getAll(param1);
        List<ObjDTO> finalList = new ArrayList<>();

        for (SomeObj someObj : allObjs){
             SomeEnum someEnum = methodcall(someObj, param1);
                 if(!SomeEnum.VALUE.equals(someEnum)){
                     finalList.add(new ObjDTO(someObj, someEnum.getMessage()));
                 }
        }
    return finalList;
    }

What i have so far:

public List<ObjDTO> getList(param1){
            List<SomeObj> allObjs = getAll(param1);
                    return allObjs.stream()
                                 .filter(someObj -> !SomeEnum.VALUE.equals(methodcall(someObj, param1)))
                                 .map(someObj -> new ObjDTO(someObj, someEnum.getMessage()))
                                 .collect(Collectors.toList());
}

The problem here is that I don't have that someEnum anymore so I need to somehow create a variable in filter() and use it inside map(). Is there a way to do this or does anyone find a better approach?

Answer 1

You can do it with a flatMap:

return allObjs.stream()
    .flatMap(someObj ->
        Stream.of(methodcall(someObj, param1))
            .filter(someEnum -> !SomeEnum.VALUE.equals(someEnum))
            .map(someEnum -> Stream.of(new ObjDTO(someObj, someEnum.getMessage()))))
    .collect(toList());