void (String[] args) { List<Float> decimals = new ArrayList<>(Arrays.asList(1.2f, 4.4f, 2.7f, 2.5f)); HashMap<Integer, List<Float>> decimalsGroupedByTheirIntegerParts = decimals.stream().collect(Collectors.toMap( Float::intValue, Collections::singletonList, (subgroup1, subgroup2) -> Stream.concat(subgroup1.stream(), subgroup2.stream()).collect(Collectors.toList()), () -> new HashMap<>() )); if (decimalsGroupedByTheirIntegerParts.isEmpty()) {} decimals.clear(); HashMap<Integer, List<Float>> decimalsGroupedByTheirIntegerParts2 = decimals.stream().collect(Collectors.toMap( Float::intValue, Collections::singletonList, (subgroup1, subgroup2) -> Stream.concat(subgroup1.stream(), subgroup2.stream()).collect(Collectors.toList()), () -> new HashMap<>() )); if (<warning descr="Condition 'decimalsGroupedByTheirIntegerParts2.isEmpty()' is always 'true'">decimalsGroupedByTheirIntegerParts2.isEmpty()</warning>) {} }