Java8 Stream List Map：Stream 流对象汇总 求和 某个属性 BigDecimal MDouble

测试实体（数字对象使用 MDouble）：
import com.mchweb.common.lang.MDouble;
import lombok.*;

@Getter
@Setter
@Builder(toBuilder = true)
@NoArgsConstructor
@AllArgsConstructor
public class User {
    private MDouble money;
}

import com.mchweb.common.lang.MDouble;
import org.apache.commons.compress.utils.Lists;

import java.util.List;

public class TestTime {

    public static void main(String[] args) {
        // 创建 一组 User对象
        List<User> list = Lists.newArrayList();
        list.add(User.builder().money(new MDouble(11D)).build());
        list.add(User.builder().money(new MDouble(22D)).build());
        list.add(User.builder().money(new MDouble(133D)).build());
        list.add(User.builder().money(new MDouble(44D)).build());

        // ★★★ 求和方法 ★★★
        MDouble dd = list.stream().map(User::getMoney).reduce(MDouble.ZERO, MDouble::add);
        System.out.println(dd);
    }
}

测试实体（数字对象使用 BigDecimal）：
import lombok.*;

import java.math.BigDecimal;

@Getter
@Setter
@Builder(toBuilder = true)
@NoArgsConstructor
@AllArgsConstructor
public class User {
    private BigDecimal money;
}

import org.apache.commons.compress.utils.Lists;

import java.math.BigDecimal;
import java.util.List;

public class TestTime {

    public static void main(String[] args) {
        // 创建 一组 User对象
        List<User> list = Lists.newArrayList();
        list.add(User.builder().money(new BigDecimal(12D)).build());
        list.add(User.builder().money(new BigDecimal(22D)).build());
        list.add(User.builder().money(new BigDecimal(133D)).build());
        list.add(User.builder().money(new BigDecimal(44D)).build());

        // ★★★ 求和方法 ★★★
        BigDecimal dd = list.stream().map(User::getMoney).reduce(BigDecimal.ZERO, BigDecimal::add);
        System.out.println(dd);
    }
}