java- how to add time properly?

My code isn't working properly for example when a user put that right now is 5 h 43 m and 7 s and the user wanna add 3 h 50 m and 57 s the code compute and shows what will be the time adding but it shows 8 h 93 m and 64 s but I want that after 60 m it shows 9 h 34 m and 4 s so can u help me out.

import java.util.Scanner;
class Main {
public static void main(String[] args) {
Scanner user_input = new Scanner (System.in);
int startup_hour;
int startup_minute;
int startup_second;
int add_hours;
int add_minutes;
int add_seconds;
System.out.print("what time is it right now(hour)? \n");
startup_hour = user_input.nextInt();
System.out.print("what time is it right now(minutes? \n");
startup_minute = user_input.nextInt();
System.out.print("what time is it right now(seconds)? \n");
startup_second = user_input.nextInt();
System.out.println("The starting time is " + startup_hour
+ " hours " + startup_minute + " minutes " + "and "
+ startup_second + " seconds \n");
System.out.print("How many hours you wanna add? \n");
add_hours = user_input.nextInt();
System.out.print("How many minutes you wanna add? \n");
add_minutes = user_input.nextInt();
System.out.print("How many seconds you wanna add? \n");
add_seconds = user_input.nextInt();
System.out.println("The user wanna add " + add_hours
+ " hours " + add_minutes + " minutes "
+ "and " + add_seconds + " seconds \n");
int totalHours = (startup_hour + add_hours);
int totalMinutes = (startup_minute + add_minutes);
int totalSeconds = (startup_second + add_seconds);
if (totalSeconds == 60){
totalMinutes++; 
totalSeconds = 0;
}
if (totalMinutes == 60){
totalHours++;
totalMinutes = 0;
}
System.out.println("After adding, the time would then be "
+ totalHours + " hours " + totalMinutes + " Minutes "
+ totalSeconds + " Seconds ");
*emphasized text*
}
}

thanku

The reason your program is not working because you are processing time, without using the standard unit, which is seconds.

For example:

Suppose the start up time is 1 hours 3 minutes and 57 seconds.
And the user want to add, 1 hour 57 minutes and 3 seconds.

The correct answer will be, 3 hours 1 Minutes 0 Seconds but your program will return 2 hours 61 Minutes 0 Seconds.

Now, why did this happen?

The reason are:

• As already stated, you did not process time using the standard unit (seconds).
• The condition in your if loop is not correct. You are only checking if the minutes/seconds are equal to 60. What if the minutes or seconds are 61 or more?

Solution:

> The simplest solution is, first convert time into seconds, add how much time you want to add, then convert it back to hours:minutes:seconds. You won't even have to use if loop if you process time using seconds.

Here is the modified code, which works properly :

import java.util.Scanner;
public class Test 
{
public static void main(String[] args)
{
Scanner user_input = new Scanner(System.in);
int startup_hour;
int startup_minute;
int startup_second;
int add_hours;
int add_minutes;
int add_seconds;
System.out.print("What time is it right now(hour)    : ");
startup_hour = user_input.nextInt();
System.out.print("What time is it right now(minutes) : ");
startup_minute = user_input.nextInt();
System.out.print("What time is it right now(seconds) : ");
startup_second = user_input.nextInt();
System.out.println("The starting time is " + startup_hour + " hours " + startup_minute + " minutes "
+ "and " + startup_second + " seconds.");
System.out.println();
System.out.print("How many hours you wanna add   : ");
add_hours = user_input.nextInt();
System.out.print("How many minutes you wanna add : ");
add_minutes = user_input.nextInt();
System.out.print("How many seconds you wanna add : ");
add_seconds = user_input.nextInt();
System.out.println("The user wanna add " + add_hours + " hours " + add_minutes + " minutes "
+ "and " + add_seconds + " seconds.");
System.out.println();
int totalSecondsAtStart = (startup_hour * 60 * 60) + (startup_minute * 60) + startup_second;
int totalSecondsToAdd = (add_hours * 60 * 60) + (add_minutes * 60) + (add_seconds);
int totalSeconds = totalSecondsAtStart + totalSecondsToAdd;
//Convert total seconds to hour, minutes and seconds;
int totalMinutes = (totalSeconds / 60);
int totalHours = (totalMinutes / 60);
int finalHours = totalHours;
int finalMinutes = totalMinutes - (totalHours * 60);
int finalSeconds = totalSeconds - (totalMinutes * 60);
System.out.println("After adding, the time would then be " + finalHours + " hours"
+ " " + finalMinutes + " Minutes " + finalSeconds + " Seconds.");
}
}

Notice how I converted time back into hours:minutes:seconds.