java stream 實現list分組求和后並取最大值

public static void main(String[] args) {

    //java stream 實現list分組求和后並取最大值
    List<HitRuleConfig> list = new ArrayList<>();
    list.add(new HitRuleConfig("1", "1", new BigDecimal(1), 1));
    list.add(new HitRuleConfig("1", "1", new BigDecimal(1), 2));
    list.add(new HitRuleConfig("2", "2", new BigDecimal(1), 3));
    list.add(new HitRuleConfig("2", "2", new BigDecimal(1), 4));
    list.add(new HitRuleConfig("1", "1", new BigDecimal(1), 5));
    list.add(new HitRuleConfig("3", "3", new BigDecimal(1), 6));
    list.add(new HitRuleConfig("3", "3", new BigDecimal(1), 7));

    Map<String, HitRuleConfig> configMap = list.parallelStream().filter(Objects::nonNull).
            collect(Collectors.groupingBy(a -> a.getAppId() + a.getTest(),
                    Collectors.collectingAndThen(Collectors.reducing((c1, c2) -> (c1.getVersionSort() > c2.getVersionSort()) ? c1 : c2), Optional::get)));

    List<HitRuleConfig> list2 = new ArrayList<>();
    configMap.forEach((k, v) -> {
        list2.add(v);
    });

    List<HitRuleConfig> list3 = new ArrayList<>();
    for (HitRuleConfig f : list2) {
        List<HitRuleConfig> collect = list.stream().filter(a -> a.getAppId().equals(f.getAppId()) && a.getTest().equals(f.getTest())).collect(Collectors.toList());
        BigDecimal reduce = collect.stream().map(HitRuleConfig::getAmount).reduce(BigDecimal.ZERO, BigDecimal::add);
        f.setAmount(reduce);
        list3.add(f);
    }

    System.out.println(list3);

}