Java-方法程序-使用带方法的开关盒

Question

我正在编写一个程序，接收用户的出生信息，年、月、日、时、分。该计划如下：

使用< code>getRangedInt方法输入一个人出生的年份(1965-2000)、月份(1-12)、日期*、小时(1-24)、分钟(1-59)。

注意：使用switch（）条件选择器结构将用户限制在其出生月份的正确天数内。例如，如果他们出生在2月[1-29]日、10月[1-31]日。提示：这里只有几个组，而不是12个不同的组！

我完全搞不懂白天的部分。除了明白我今天应该做什么，我已经设法让其他一切都开始工作了。

我的代码：

public static void main(String[] args) 
{
    int year, month, day, hour, minutes;
    String msg="";
    boolean done = true;
    Scanner in = new Scanner(System.in);

    while(done)
    {
        year = SafeInput.getIntInRange(in, "Enter the year you were born: ", 1965, 2000);       
        month = SafeInput.getIntInRange(in, "Enter your month of birth: ", 1, 12);
        day = SafeInput.getIntInRange(in, "Enter the day you were born: ", day, day);      
        hour = SafeInput.getIntInRange(in, "Enter the hour you were born in: ", 1, 24);
        minutes = SafeInput.getIntInRange(in, "Enter the minutes you were born: ", 1, 59);

        System.out.println("You were born: " + year + " , " + msg + " , " + hour + " hr. " + minutes + " mins. ");

        done = SafeInput.getYNConfirm(in, "Would you like to play again?");
    }
}

getIntInRange只是做一个基本的输入来获取范围内的数字。我很困惑，因为我不知道如何做当天的范围，因为也应该使用开关。

Answer 1

您的日范围取决于用户输入的上一个月编号，因此您必须检查该编号才能知道要显示的日期范围。提示告诉您的是，您不需要每个月都有不同的有效天数范围，因为某些月份共享相同的范围。以下是一个月的天数：

January     31
February    28/29
March       31
April       30
May         31
June        30
July        31
August      31
September   30
October     31
November    30
December    31

如您所见，只有3个组，任务要求您在＜code＞开关中不＜code＞中断＜/code＞时利用故障排除：

int upperDaysLimit;
switch(month) {
    case 1:
    case 3:
    case 5:
    //...
    case 12: upperDaysLimit = 31;
             break;
    case 4:
    case 6:
    // and so on
}

现在，您可以在查询天数时使用该范围限制：

day = SafeInput.getIntInRange(in, "Enter the day you were born: ", 1, upperDaysLimit);

Answer 2

在这里，您的一天取决于输入的月份。因此，首先您需要像现在这样将用户输入的月份作为一个整数，并继续在一个开关中使用该数字:

int month = 0;
int numberOfDays;

        switch (month) {
            case 1:  numberOfDays = DaysInJanuary;
                     break;
            case 2:  numberOfDays = DaysInFebruary;
                     break;
            case 3:  numberOfDays = DaysInMarch;
                     break;
            case 4:  numberOfDays = DaysInApril;
                     break;
            case 5:  numberOfDays = DaysInMay;
                     break;
            case 6:  numberOfDays = DaysInJune;
                     break;
            case 7:  numberOfDays = DaysInJuly;
                     break;
            case 8:  numberOfDays = DaysInAugust;
                     break;
            case 9:  numberOfDays = DaysInSeptember;
                     break;
            case 10: numberOfDays = DaysInOctober;
                     break;
            case 11: numberOfDays = DaysInNovember;
                     break;
            case 12: numberOfDays = DaysInDecember;
                     break;
            default: throw new IllegalArgumentException("Not a valid month");
                     break;
        }

然后，您可以继续为“最大日”范围设置变量。

day = SafeInput.getIntInRange(in, "Enter the day you were born: ", 1, numberOfDays);

希望这有帮助。

Answer 3

这是一个非常奇怪的要求。

它看起来像什么是从你看起来像这样的东西：

int numberOfDays;
switch (month) {
case 1: // $FALL-THROUGH
case 3: // $FALL-THROUGH
case 5: // $FALL-THROUGH
case 7: // $FALL-THROUGH
case 9: // $FALL-THROUGH
case 11:
    numberOfDays = 31;
    break;
case 4: // $FALL-THROUGH
case 6: // $FALL-THROUGH
case 8: // $FALL-THROUGH
case 10: // $FALL-THROUGH
case 12:
    numberOfDays = 30;
    break;
case 2:
    numberOfDays = (0 == year / 4) ? 29 : 28;
    break;
default:
    throw new IllegalArgumentException("month not 1-12");
} // switch (too long for my liking)

然后呢

day = SafeInput.getIntInRange(in, "Enter the day you were born: ", 1, numberOfDays);

这利用了交换机中可用的贯穿构造，因此如果您满足条件，您将执行直到返回语句（或中断/抛出）。

请记住，替代方案是：

private static final Set<Integer> MONTHS_30_DAYS = Sets.newTreeSet(4, 6, 8, 10, 12);
private static final Set<Integer> MONTHS_31_DAYS = Sets.newTreeSet(1, 3, 5, 7, 9, 11);

public static int numberOfDays(int month, int year) {
   if (MONTHS_30_DAYS.contains(month)) {
      return 30;
   } else if (MONTHS_31_DAYS.contains(month)) {
      return 31;
   } else {
     return (0 == year / 4) ? 29 : 28;
   }
}