Convert integer minutes into String "hh:mm"

Here you go:

/*Output: 02:05 */
public String fromMinutesToHHmm(int minutes) {
    long hours = TimeUnit.MINUTES.toHours(Long.valueOf(minutes));
    long remainMinutes = min - TimeUnit.HOURS.toMinutes(hours);
    return String.format("%02d:%02d", hours, remainMinutes);
}

Kotlin version

class DateUtils {

    companion object {

        fun fromMinutesToHHmm(minutes: Int): String {
            val hours = TimeUnit.MINUTES.toHours(minutes.toLong())
            val remainMinutes = minutes - TimeUnit.HOURS.toMinutes(hours)
            return String.format("%02d:%02d", hours, remainMinutes)
        }

    }

}

String startTime = "00:00";
int minutes = 120;
int h = minutes / 60 + Integer.parseInt(startTime.substring(0,1));
int m = minutes % 60 + Integer.parseInt(startTime.substring(3,4));
String newtime = h+":"+m;

int minutes = 120;

int h = minutes / 60;
int m = minutes % 60;

String.format("%02d:%02d",h,m); // output : "02:00"
String.format("%d:%d",h,m); // output : "2:0"