Trying to build a clock class, but AM/PM doesn't change if the starting hour is 12 (JAVA)

This class is supposed to create a clock and I'm trying to make a method so you can advance x amount of minutes. The method works fine except for when the initial hour is 12:00, when this happens I always get AM/PM wrong.

public void advance(int a){
int m =a%60; //Minutes to add
int h =a/60; //Hours to add
minute = minute + m; //Add minutes to m
while(minute>=60) { //Divides minutes by 60 to get the amount of hours in case the input is bigger than 60
    minute = minute - 60;
    h++;
}

// Test if OG hour = 12
if(hour==12){
    hour=0;
    if(h<12) {
        amPm = amPm; 
        hour = hour + h;
    }
    if(h>=12)
        if(amPm.equals("AM")) {
            amPm = "PM";
            hour = hour + h;
        }        
    else 
        if(amPm.equals("AM")) {
            amPm = "PM";
            hour = hour + h;
        }          
    if(hour==0)
        hour=12;        
} else {
    hour = hour + h;
    while(hour>12) { 
    if(amPm.equals("AM")) {
        amPm = "PM";
    } else
        amPm = "AM";
    hour = hour - 12;
}
}   

}