写一段Java实现首先，我们需要定义一个亿万富翁类，该类包含以下属性：姓名、到达日期、城市、财富。接着，我们需要从文件中读取所有亿万富翁信息，创建一个亿万富翁对象数组。 接下来，我们可以使用Java的排序算法（如快速排序）将亿万富翁按照到达日期排序，使得最早到达的亿万富翁排在最前面。 然后，我们可以遍历亿万富翁数组，计算每个城市每天的财富总和。我们可以使用一个哈希表来存储每个城市每天的财富总和，其中哈希表的键为日期和城市组成的字符串（例如“2022-01-01-北京”），哈希表的值为财富总和。对于每个亿万富翁，我们可以通过计算其到达日期与之前到达日期的差值，将其财富平均分配到这段时间内的每一天。然后，我们可以将分配得到的财富加入对应的哈希表键中的值中。 最后，我们可以输出每个城市每天的财富总和，以及按照到达日期排序后的亿万富翁列表。

好的，下面是一段Java代码实现：

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Scanner;

public class Billionaire {
    private String name;
    private String arriveDate;
    private String city;
    private double wealth;

    public Billionaire(String name, String arriveDate, String city, double wealth) {
        this.name = name;
        this.arriveDate = arriveDate;
        this.city = city;
        this.wealth = wealth;
    }

    public String getName() {
        return name;
    }

    public String getArriveDate() {
        return arriveDate;
    }

    public String getCity() {
        return city;
    }

    public double getWealth() {
        return wealth;
    }

    public static void main(String[] args) {
        // 从文件中读取亿万富翁信息
        String filename = "billionaires.txt";
        Billionaire[] billionaires = readBillionairesFromFile(filename);

        // 按照到达日期排序
        Arrays.sort(billionaires, (a, b) -> a.getArriveDate().compareTo(b.getArriveDate()));

        // 计算每个城市每天的财富总和
        HashMap<String, Double> cityWealthMap = new HashMap<>();
        String prevDate = "";
        for (Billionaire billionaire : billionaires) {
            String cityDateKey = billionaire.getArriveDate() + "-" + billionaire.getCity();
            if (!cityWealthMap.containsKey(cityDateKey)) {
                cityWealthMap.put(cityDateKey, 0.0);
            }
            if (!prevDate.equals("")) {
                double wealthPerDay = billionaire.getWealth() / daysBetween(prevDate, billionaire.getArriveDate());
                for (String dateKey : getDateKeysBetween(prevDate, billionaire.getArriveDate(), billionaire.getCity())) {
                    cityWealthMap.put(dateKey, cityWealthMap.get(dateKey) + wealthPerDay);
                }
            }
            prevDate = billionaire.getArriveDate();
        }

        // 输出每个城市每天的财富总和
        for (String cityDateKey : cityWealthMap.keySet()) {
            System.out.println(cityDateKey + ": " + cityWealthMap.get(cityDateKey));
        }

        // 输出按照到达日期排序后的亿万富翁列表
        for (Billionaire billionaire : billionaires) {
            System.out.println(billionaire.getName() + ": " + billionaire.getArriveDate() + " " + billionaire.getCity() + " " + billionaire.getWealth());
        }
    }

    // 从文件中读取亿万富翁信息
    private static Billionaire[] readBillionairesFromFile(String filename) {
        try {
            Scanner scanner = new Scanner(new File(filename));
            int n = scanner.nextInt();
            scanner.nextLine(); // 读取换行符
            Billionaire[] billionaires = new Billionaire[n];
            for (int i = 0; i < n; i++) {
                String line = scanner.nextLine();
                String[] parts = line.split(" ");
                billionaires[i] = new Billionaire(parts[0], parts[1], parts[2], Double.parseDouble(parts[3]));
            }
            scanner.close();
            return billionaires;
        } catch (FileNotFoundException e) {
            e.printStackTrace();
            return null;
        }
    }

    // 计算两个日期之间相差的天数
    private static int daysBetween(String date1, String date2) {
        int year1 = Integer.parseInt(date1.substring(0, 4));
        int month1 = Integer.parseInt(date1.substring(5, 7));
        int day1 = Integer.parseInt(date1.substring(8, 10));
        int year2 = Integer.parseInt(date2.substring(0, 4));
        int month2 = Integer.parseInt(date2.substring(5, 7));
        int day2 = Integer.parseInt(date2.substring(8, 10));
        int days1 = getDaysFromYearStart(year1, month1, day1);
        int days2 = getDaysFromYearStart(year2, month2, day2);
        return Math.abs(days2 - days1);
    }

    // 计算某年某月某日是该年的第几天
    private static int getDaysFromYearStart(int year, int month, int day) {
        int[] daysInMonth = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
        int days = day;
        for (int i = 1; i < month; i++) {
            days += daysInMonth[i];
        }
        if (month > 2 && isLeapYear(year)) {
            days++;
        }
        return days;
    }

    // 判断某年是否为闰年
    private static boolean isLeapYear(int year) {
        return (year % 4 == 0 && year % 100 != 0) || year % 400 == 0;
    }

    // 获取两个日期之间的所有日期对应的哈希表键
    private static String[] getDateKeysBetween(String date1, String date2, String city) {
        int year1 = Integer.parseInt(date1.substring(0, 4));
        int month1 = Integer.parseInt(date1.substring(5, 7));
        int day1 = Integer.parseInt(date1.substring(8, 10));
        int year2 = Integer.parseInt(date2.substring(0, 4));
        int month2 = Integer.parseInt(date2.substring(5, 7));
        int day2 = Integer.parseInt(date2.substring(8, 10));
        int days1 = getDaysFromYearStart(year1, month1, day1);
        int days2 = getDaysFromYearStart(year2, month2, day2);
        int diff = days2 - days1;
        String[] dateKeys = new String[diff + 1];
        for (int i = 0; i <= diff; i++) {
            int currYear = year1;
            int currMonth = month1;
            int currDay = day1 + i;
            if (currDay > 31 && (currMonth == 1 || currMonth == 3 || currMonth == 5 || currMonth == 7 || currMonth == 8 || currMonth == 10 || currMonth == 12)) {
                currDay -= 31;
                currMonth++;
            } else if (currDay > 30 && (currMonth == 4 || currMonth == 6 || currMonth == 9 || currMonth == 11)) {
                currDay -= 30;
                currMonth++;
            } else if (currDay > 28 && currMonth == 2 && !isLeapYear(currYear)) {
                currDay -= 28;
                currMonth++;
            } else if (currDay > 29 && currMonth == 2 && isLeapYear(currYear)) {
                currDay -= 29;
                currMonth++;
            }
            if (currMonth > 12) {
                currMonth = 1;
                currYear++;
            }
            dateKeys[i] = String.format("%04d-%02d-%02d-%s", currYear, currMonth, currDay, city);
        }
        return dateKeys;
    }
}

请注意，上述代码只是一个示例，可能需要根据实际情况进行修改和优化。