I'm sure there's a really easy explanation to this, but I've been programming
all day (or trying to) and by now, my mind has started to melt! I'm using
BlueJ btw!

I'm trying to display available slots in a day, which come as half hour
periods.
The code below takes the start of the day as being an integer (9) and the end
of the day as an integer also (17). It should then split the day up into 16
sections and output them to the terminal as:
09:00
09:30
10:00
...
16:30

To do this, I have set up two strings, one for hours (hour!) and one for
minutes (minute!). These strings are formed by two integers, one is limit,
which is used as the limit for the loop as well as the hour, and the other is
min, incremented in batches of 30, then reset to 0 instead of reaching 60.
When "min" is "0", "limit" is incremented.
To make it into 24 hour format, if "limit" is < 10, an extra 0 is added to
the string "hour" and if "min" is 0, an extra 0 is added to the string
"minute".
If someone could tell me why this is not outputting to the terminal it would
really help.

    public void showAppointments()
    {
       String hour = ("");
       int min = 0;
       String minute = ("");
        for(int limit = 9; limit > 17; ) {
           hour = ("");
           minute = ("");
           if ((limit - 10) < 0) {
               hour = ("0" + limit);
           }
           else {
               hour = ("" + limit);
           }
           if (min == 0) {
               minute = ("0" + min);
           }
           else {
               minute = ("" + min);
           }

           System.out.println(hour + ":" + minute);
           
           min = min + 30;
           if (min == 60) {
               min = 0;
           }
           if (min == 0) {
               limit++;
           }
        }
    }