根据单个条件去重
list.stream().collect(
        Collectors.collectingAndThen(
                Collectors.toCollection(
                        () -> new TreeSet<>(
                                Comparator.comparing(Class::getParams)))
                , ArrayList::new));

根据多条件去重

list.stream().collect(
        Collectors.collectingAndThen(
                Collectors.toCollection(
                        () -> new TreeSet<>(
                                Comparator.comparing(a->a.getParam1+";"+a.getParam2)))
                , ArrayList::new));

流去重