Getting incorrect result when checking a date between two other dates in Java

问题

I'm using the code below to check if an hour is between two other specific hours:

String openHour = "08:00 AM";
String currentHour = "10:00 PM";
String closeHour = "11:00 PM"; //Change to 02:00 AM doesn't work!!!

SimpleDateFormat format = new SimpleDateFormat("hh:mm a");
Date openHourDate = format.parse(openHour);
Date currentHourDate = format.parse(currentHour);
Date closeHourDate = format.parse(closeHour);

Calendar openCalendar = Calendar.getInstance();
openCalendar.setTime(openHourDate);

Calendar currentCalendar = Calendar.getInstance();
currentCalendar.setTime(currentHourDate);

Calendar closeCalendar = Calendar.getInstance();
closeCalendar.setTime(closeHourDate);

Date open = openCalendar.getTime();
Date current = currentCalendar.getTime();
Date close = closeCalendar.getTime();

if (current.after(open) && current.before(close)) {
    System.out.println("Correct!");
} else {
    System.out.println("Incorrect!");
}

If the currentHour is "10:00 PM" as you see in my code, everything works fine but if I change the change it to "02:00 AM", the code doesn't work as expected even if the currentHour is between 08:00 AM and 02:00 AM. How to solve this?

回答1:

Here is a solution using LocalTime that also correctly handles current and closing time being after midnight.

String openHour = "08:00 AM";
String currentHour = "01:00 PM";
String closeHour = "02:00 AM";

DateTimeFormatter formatter = DateTimeFormatter.ofPattern( "hh:mm a" , Locale.US );
LocalTime openTime = LocalTime.parse(openHour, formatter);
LocalTime currentTime  = LocalTime.parse(currentHour, formatter);
LocalTime closeTime = LocalTime.parse(closeHour, formatter);

boolean isOpen = false;
if (closeTime.isAfter(openTime)) {
  if (openTime.isBefore(currentTime) && closeTime.isAfter(currentTime)) {
    isOpen = true;
  }
} else if (currentTime.isAfter(openTime) || currentTime.isBefore(closeTime)) {
  isOpen = true;
}

if (isOpen) {
  System.out.println("We are open");
} else {
  System.out.println("We are closed");
}

回答2:

Just need to roll the day, as Michael Platt suggested:

import java.util.*;
import java.text.*;

public class Foo {
  public static void main(String[] args) throws Exception {

    String openHour = "08:00 AM";
    String currentHour = "10:00 PM";
    String closeHour = "11:00 PM"; //Change to 02:00 AM doesn't work!!!

    SimpleDateFormat format = new SimpleDateFormat("hh:mm a");
    Date openHourDate = format.parse(openHour);
    Date currentHourDate = format.parse(currentHour);
    Date closeHourDate = format.parse(closeHour);

    Calendar openCalendar = Calendar.getInstance();
    openCalendar.setTime(openHourDate);

    Calendar currentCalendar = Calendar.getInstance();
    currentCalendar.setTime(currentHourDate);

    Calendar closeCalendar = Calendar.getInstance();
    closeCalendar.setTime(closeHourDate);

    if (closeCalendar.before(openCalendar)) {
      closeCalendar.add(Calendar.DAY_OF_YEAR, 1);
    }

    Date open = openCalendar.getTime();
    Date current = currentCalendar.getTime();
    Date close = closeCalendar.getTime();

    if (current.after(open) && current.before(close)) {
      System.out.println("Correct!");
    } else {
      System.out.println("Incorrect!");
    }
  }
}

来源：https://stackoverflow.com/questions/55599273/getting-incorrect-result-when-checking-a-date-between-two-other-dates-in-java

标签

java

java-8

java-time

java-date

java-calendar