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java - 如何从我的数组列表中返回最近加入的成员？

问题描述

我正在尝试查找最近加入我的健身俱乐部人员列表的成员。我的思考过程是找到最高的年份，然后是最高的月份，但我在执行它时遇到了麻烦。

以下是俱乐部成员：

club.join(new Membership("Ellen", 2, 2016, 115.00));
        club.join(new Membership("Eric", 1, 2017, 75.00));
        club.join(new Membership("Ben", 3, 2015, 35.50));
        club.join(new Membership("Matt", 12, 2014, 42.00));
        club.join(new Membership("Luke", 5, 2010, 145.00));
        club.join(new Membership("Jon", 6, 2017, 65.00));
        club.join(new Membership("Ryan", 7, 2016, 0.00));
        club.join(new Membership("Alan", 8, 2015, 195.00));
        club.join(new Membership("Jaden", 9, 2015, 15.00));
        club.join(new Membership("Dan P", 10, 2011, 25.00));
        club.join(new Membership("Jack", 2, 2013, 80.75));
        club.join(new Membership("Mrs. R", 1, 2014, 125.00));
        club.join(new Membership("Dan S", 1, 2015, 45.00));
        club.join(new Membership("Caleb", 10, 2016, 0.00));
        club.join(new Membership("Jacob", 5, 2017, 10.00));
        club.join(new Membership("Anny", 7, 2016, 110.00));
        club.join(new Membership("Wendy", 7, 2015, 85.00));
        club.join(new Membership("Natalie", 8, 2014, 0.00));
        club.join(new Membership("Paul", 9, 2016, 20.00));
        club.join(new Membership("Zuck", 10, 2017, 55.00));

这是我查找最新方法的代码：

int tempMonth = 13;
        int tempYear = 3000;
        ArrayList<Membership> ppl = new ArrayList<Membership>();
        Iterator<Membership> itr = members.iterator();
        while(itr.hasNext())
        {
            Membership item = itr.next();
            if(members.size() == 0)
            {
                return null;
            }
            else
            {
                if(tempYear > item.getYear())
                {
                    if(tempMonth > item.getMonth())
                    {
                        ppl.add(item);
                        itr.remove();
                    }
                }
            }
        }
        return ppl;

标签： javaloopsiterator

解决方案

您可以使用Collections.max和自定义Comparator对列表进行排序Membership

Collections.max(members, Comparator.comparing(Membership::getYear)
                                   .thenComparing(Membership::getMonth));

您也可以使用stream

members.stream().max(//comparator)

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