java - Joda-Time - 天数不增加

Question

这是一个学校项目。

代码如下:

// get the remaining available hours
public int getAvailableHours(Subject sub) {

    DateTime dt = new DateTime();
    int hours = 0;

    int mondays = 0;
    int tuesdays = 0;
    int wednesdays = 0;
    int thursdays = 0;
    int fridays = 0;
    int saturdays = 0;
    int sundays = 0;

    if(sub != null) {
        if(!sub.getExamDate().isBefore(dt)) {
            int days = Days.daysBetween(dt, sub.getExamDate()).getDays(); 

            // DEBUGGING - take out
            System.out.println(days);
            System.out.println(dt);
            System.out.println(sub.getExamDate());

            DateTime day = new DateTime();
            for(int i = 1; i < days; i++) {
                day.plusDays(i);

                // DEBUGGING - take out
                System.out.println(day.dayOfWeek().getAsText());
                System.out.println(day.dayOfMonth().getAsText());

                switch(day.dayOfWeek().getAsText()) {
                    case "Monday":
                        mondays++;
                        break;
                    case "Tuesday":
                        tuesdays++;
                        break;
                    case "Wednesday":
                        wednesdays++;
                        break;
                    case "Thursday":
                        thursdays++;
                        break;
                    case "Friday":
                        fridays++;
                        break;
                    case "Saturday":
                        saturdays++;
                        break;
                    case "Sunday":
                        sundays++;
                        break;
                    default:

                        break;
                }
            }
            hours = (mondays * hoursOnMonday) + (tuesdays * hoursOnTuesday) + 
                    (wednesdays * hoursOnWednesday) + (thursdays * hoursOnThursday)
                    + (fridays * hoursOnFriday) + (saturdays * hoursOnSaturday) 
                    + (sundays * hoursOnSunday);
        }
    }

    return hours;
}

我想做的是创建一个学习时间表调度程序。我的程序中有一部分允许用户输入他们每天想学习多长时间。所以我在上面做的是遍历有多少天，看看每天有多少天发生(所以，从现在到该科目的考试日期之间有多少个星期一、星期二等)，这样我就可以计算出有多少天用户必须学习的总小时数。

但是现在，我尝试遍历它，它总是返回“星期三”，它没有递增。今天，在南非，是 10 月 1 日星期三，但该应用程序现在似乎确实增加了这一天，以意识到它正在查看 10 月 2 日星期四(明天)。我认为问题出在这一行:day.plusDays(i);，但我不知道解决它的方法。

Answer 1

它是不可变的实例，所以你必须把它抓回来

day = day.plusDays(i);

This datetime instance is immutable and unaffected by this method call. from doc