Java - How to check is a LocalTime object is before midnight

I am trying to determine if a particular LocalTime is before Midnight. Background basically I want to know if a shift's start/end time bleed over into the next day. For example if a shift was scheduled for 23:00 - 07:00, then this would be considered bleeding into the next day since the end time is after midnight and the start time is before.

I began to implement this by seeing if the start time is before midnight, and seeing if the end time is after midnight. This would meet the criteria of being overlapping into the next day.

In Java my code looks like this

public boolean checkTime() {
        
        final LocalTime startTime = LocalTime.parse("23:00");
        final LocalTime endTime = LocalTime.parse("07:00");

        return startTime.isBefore(LocalTime.MIDNIGHT) //false
                && endTime.isAfter(LocalTime.MIDNIGHT)) //true;
}

Why does it return false for the start time being not before midnight? Isn't the time of 23:00 one hour before midnight? I would expect this to return true. Maybe I am misunderstanding something? I am working with LocalTimes and not using LocalDateTimes

According to the documentation, for both isBefore and isAfter:

> The comparison is based on the time-line position of the time within a day.

These methods assume that the times you are comparing are on the same day, so you cannot use these to check if the period "bleeds into" the second day.

Assuming a shift must be less than 24 hours, you can check if it "bleeds into" the second day by checking if the end is before the start. This takes advantage of this "assuming the two times are in the same day" characteristic of isBefore. If isBefore thinks that endTime is before startTime, that must mean endTime is in the next day.

endTime.isBefore(startTime)

As with all things, when in doubt, check the documentation.

Here is the documentation for the various parts of your code.

• LocalTime#parse(String)
• LocalTime#MIDNIGHT
• LocalTime#isBefore(LocalTime)

The important one is the LocalTime::isBefore method. Look at what it says.

Checks if this time is before the specified time. The comparison is based on the time-line position of the time within a day.

That bolded part isn't completely clear, but what that means is that, it is going to ask if 23 is before 0 on the same day.

More specifically, if May 18 23:00 is before May 18 00:00. As you can see, the answer is false because you accidentally asked for the same day.

You need to use a different tool, likely LocalDateTime, to be able to solve this problem. Let me know if you have trouble using that tool instead and I can post an example.

LocalTime only knows the time. It doesn't know anything about the date. LocalTime.MIDNIGHT is The time of midnight at the start of the day, '00:00'.. That's the reason why your code is working like that.

startTime.isBefore(LocalTime.MIDNIGHT) == false

because 23:00 is after 00:00.

In the case of

endTime.isAfter(LocalTime.MIDNIGHT)) == true

because 7:00 is after 00:00

You should consider to use LocalDateTime