日历类“正常”日期问题

Question

我正在开发一个程序，该程序将成为一个基本功能，如果用户可以检查某些内容，并且该程序将计算截止日期，为简单起见，将在 7 天后。 此函数在其他类中使用，今天已在使用它的类中如此定义

today=Calendar.getInstance();

我正在使用 Calendar 类来执行此操作。 一开始我试过这个

  public Calendar getReturnDate()
  {
   Calendar dueDate = Calendar.getInstance();
   dueDate.set(today.MONTH, today.get(today.MONTH));
   dueDate.set(today.YEAR, today.get(today.YEAR));
   dueDate.add(today.DATE,today.get(today.DATE + 7));

   return dueDate;
}

这给了我一个结果，所有内容都打印到毫秒。

所以我研究了 Calendar 类，发现 .add 方法可以完成这项工作......或者我是这么认为的。下面是代码

    public Calendar getReturnDate()
{
   Calendar dueDate = Calendar.getInstance();
   dueDate.set(today.MONTH, today.get(today.MONTH));
   dueDate.set(today.YEAR, today.get(today.YEAR));
   dueDate.add(today.DATE,7);

   return dueDate;
}

当在下面的代码中调用该函数时，会发生下面的打印。

    public String toString()
 {
     //Prints them out
     String str = "The specs of the book are: ";
     str+= "\n\t Title: " + title;
     str+= "\n\t Author: " + year;
     str += "\n\t checkout date: " + (getReturnDate().MONTH+1) + "/" + getReturnDate().DATE;
     return str;
 }

结果：

 Title: ABC
 Author: Suzie Smith
 checkout date: java.util.GregorianCalendar[time=1428600973310,areFieldsSet=true,areAllFieldsSet=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="America/New_York",offset=-18000000,dstSavings=3600000,useDaylight=true,transitions=235,lastRule=java.util.SimpleTimeZone[id=America/New_York,offset=-18000000,dstSavings=3600000,useDaylight=true,startYear=0,startMode=3,startMonth=2,startDay=8,startDayOfWeek=1,startTime=7200000,startTimeMode=0,endMode=3,endMonth=10,endDay=1,endDayOfWeek=1,endTime=7200000,endTimeMode=0]],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=2015,MONTH=3,WEEK_OF_YEAR=15,WEEK_OF_MONTH=2,DAY_OF_MONTH=9,DAY_OF_YEAR=99,DAY_OF_WEEK=5,DAY_OF_WEEK_IN_MONTH=2,AM_PM=1,HOUR=1,HOUR_OF_DAY=13,MINUTE=36,SECOND=13,MILLISECOND=310,ZONE_OFFSET=-18000000,DST_OFFSET=3600000]

如您所见，它运行不正常。当我在上面的代码中调用此方法时，我希望它打印出月/年。

有谁知道怎么做或者为什么我的不工作？

来源： https://docs.oracle.com/javase/7/docs/api/java/util/GregorianCalendar.html

Answer 1

public String toString() {
    Calendar returnDate = getReturnDate();
    // Prints them out
    String str = "The specs of the book are: ";
    str += "\n\t Title: " + title;
    str += "\n\t Author: " + year;
    str += "\n\t checkout date: " + (returnDate.get(Calendar.MONTH) + 1) + "/" + returnDate.get(Calendar.DATE);
    return str;
}