You can add hours, minutes, seconds and nanoseconds:
LocalTime time = LocalTime.now();
LocalTime addHours = time.plusHours(5); // Add 5 hours
LocaLTime addMinutes = time.plusMinutes(15) // Add 15 minutes
LocalTime addSeconds = time.plusSeconds(30) // Add 30 seconds
LocalTime addNanoseconds = time.plusNanos(150_000_000) // Add 150.000.000ns (150ms)