java - 比较两个包含日期的字符串以检查其中一个是在另一个之前还是之后

Question

我已经为客户端-服务器应用程序编写了一些代码，它允许服务器为 2 个不同的项目设置 2 个截止日期。这些项目有一个截止时间，当时间到达时服务器应显示该截止时间。

这是我到目前为止所拥有的:

String[] deadlines = new String[2];

Calendar deadline = Calendar.getInstance();

for(int i = 0; i < 2; i++)
{

    System.out.print("Enter finishing time for item " + (i+1) + " in 24-hr format "); // Item 1
    System.out.print("(e.g. 17:52) :  ");
    String timeString = input.nextLine(); // get input

    String hourString = timeString.substring(0,2);
    int hour = Integer.parseInt(hourString);

    String minString = timeString.substring(3,5);
    int minute = Integer.parseInt(minString);                   

    deadline.set(year,month,date,hour,minute,0);

    deadlines[i] = getDateTime(deadline);

    System.out.print("\nDeadline set for item " + (i+1) + "\n");
    System.out.println(getDateTime(deadline)+ "\n\n");
}

System.out.println("\nServer running...\n");


Calendar now = Calendar.getInstance();

System.out.print(deadlines[0]); // HERE
System.out.print(deadlines[1]); // AND HERE
// getDateTime(now) outputs the same as deadlines[0] + deadlines[1].


while(now.before(deadlines[0]) || now.before(deadlines[1])) // THIS LINE
{
    //System.out.println(getDateTime(now));

    try
    {
        Thread.sleep(2000);
    }
    catch (InterruptedException intEx)
    {

    }

    now = Calendar.getInstance();

    if (now.after(deadlines[0]))
        System.out.println("\n\nDeadline reached" + deadlines[0] + "\n");
    if (now.after(deadlines[1]))
        System.out.println("\n\nDeadline reached" + deadlines[1] + "\n");
}

public static String getDateTime(Calendar dateTime)
{
    //Extract hours and minutes, each with 2 digits
    //(i.e., with leading zeroes if needed)...

    String hour2Digits = String.format("%02d", dateTime.get(Calendar.HOUR_OF_DAY));
    String min2Digits = String.format("%02d", dateTime.get(Calendar.MINUTE));

    return(dateTime.get(Calendar.DATE) 
            + "/" + (dateTime.get(Calendar.MONTH)+1) 
            + "/" + dateTime.get(Calendar.YEAR) 
            + "  "+ hour2Digits + ":" + min2Digits);
}   

我需要检查 now 是否早于 deadlines[0] 和 deadlines[1] 的值。我怎样才能做到这一点？一定有比将其转换为字符串等更好的方法吗？

Answer 1

您可以使用LocalTime#parse，它采用您希望用户输入的确切格式。

String input = "17:52";
LocalTime lt = LocalTime.parse(input); // 17:52

然后将其传递给带有 LocalDate 的 LocalDateTime#of

LocalDateTime ldt = LocalDateTime.of(LocalDate.of(year, month, day), lt);

如果需要比较它们，请使用 compare()、isAfter() 或 isBefore()

while (LocalDateTime.now().isAfter(ldt)){
    // doStuff
}

<小时/>

编辑

如果您想访问循环外部的对象，请继续使用相同的数组逻辑。

LocalDateTime[] dateTimes = new LocalDateTime[2];

for (//){
    datesTimes[i] // for example
}