int arrSize = 100;
int[] arr = new Random().ints(arrSize, -10, 10).toArray();

Arrays.stream(arr).boxed().map(Integer::signum).
            collect(Collectors.groupingBy(Function.identity(),
                    Collectors.collectingAndThen(Collectors.counting(), count -> (double) count / arrSize))).
            entrySet().stream().sorted(Map.Entry.comparingByKey()).forEach(System.out::println);