java8計算list對象BigDecimal屬性的最大值、最小值、總和、平均值

代碼舉例

@Slf4j
public class TestList {
    @Test
    public void test01() throws IOException {
        User user1 = new User(2, "Steven", "@sun123", new Date(), 2000.0, new BigDecimal(2000));
        User user2 = new User(3, "Steven", "@sun123", new Date(), 3000.0, new BigDecimal(3000));
        User user3 = new User(4, "Steven", "@sun123", new Date(), 4000.0, new BigDecimal(4000));
        List<User> userList = new ArrayList<>();
        userList.add(user1);
        userList.add(user2);
        userList.add(user3);
        //求最大值
        BigDecimal max = userList.stream().map(User::getWeight).max((x1, x2) -> x1.compareTo(x2)).get();
        //求最小值
        BigDecimal min = userList.stream().map(User::getWeight).min((x1, x2) -> x1.compareTo(x2)).get();
        //求和
        BigDecimal sum = userList.stream().map(User::getWeight).reduce(BigDecimal.ZERO, BigDecimal::add);
        //求平均值
        BigDecimal average = userList.stream().map(User::getWeight).reduce(BigDecimal.ZERO, BigDecimal::add).divide(BigDecimal.valueOf(userList.size()), 2, BigDecimal.ROUND_HALF_UP);

        log.info(max.toString());
        log.info(min.toString());
        log.info(sum.toString());
        log.info(average.toString());
    }
}

輸出結果

10:43:59.260 [main] INFO TestList - 4000
10:43:59.267 [main] INFO TestList - 2000
10:43:59.267 [main] INFO TestList - 9000
10:43:59.267 [main] INFO TestList - 3000.00