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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.

Print the formula used to describe the addition of two numbers

I am stuck in the U of Helsinki Java MOOC:
Create a program that can be used to add two integers together. In the beginning, the user is asked to give two integers that are to be summed. The program then prints the formula that describes the addition of the numbers.
Example output:
Give the first number:
5
Give the second number:
4
5 + 4 = 9
I am trying to get the system to print " "first" + "second" is "result". For some reason I am stumped on this otherwise easy question. My code is always throwing an error. What am I doing wrong in the last line?
import java.util.Scanner;
public class AdditionFormula {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
// write your program here
System.out.println("Give the first number: ");
int first = Integer.valueOf(scanner.nextLine());
System.out.println("Give the second number: ");
int second = Integer.valueOf(scanner.nextLine());
//System.out.println("first" " + " Integer.valueOf(first) + Integer.valueOf(second));
System.out.println(first + " + " + second " = " + (first + second));
}

The code you provided does not compile
Change to
System.out.println(first + " + " + second + " = " + (first + second));

Error When Printing a Large Number, Min and Sec Become Negative

I am getting an error when printing a large number, minutes and seconds become negative. I think it is due to the size of the number that is printing.
import java.util.Scanner;
public class Minutes
{
public static void main(String[] args)
{
//User information
Scanner in = new Scanner(System.in);
System.out.println("Please enter a number of hours, days, weeks or years: ");
int s = in.nextInt();
//Compute input
int hours = s * 60;
int days = s * 1440;
int weeks = s * 10080;
int years = s * 525600;
//Print results
System.out.println("------------------------------------------------");
System.out.println("Here are your results!");
System.out.println("If you entered hours, this is the number of minutes" + ": " + hours);
System.out.println("If you entered days, this is the number of minutes" + ": " + days);
System.out.println("If you entered weeks, this is the number of minutes" + ": " + weeks);
System.out.println("If you entered years, this is the number of minutes" + ": " + years);
}
}

Thats exactly it, you are having a integer overflow, when that happens, java starts the count from the Integer.MIN_VALUE that why i shows negative, convert it to long ant it should be fine.

Displaying an output decimal with 2 places in java

I'm trying to find out why the %.2f declaration when outputting a decimal isn't working in my code, I've checked other similar questions but I can't seem to locate the issue in the specific logic error I'm receiving. When I go to compile my program it compiles fine, I go to run it and everything outputs fine until I get to the final cost where I'm trying to only display that decimal value with 2 decimal places.
I get an exception in thread "main"
Java.util.illegalformatconversionexception f! = Java.lang.string
At java.util.Formatter$formatspecifier.failconversion(Unknown Source)
At java.util.Formatter$formatspecifier.printFloat(Unknown Source)
At java.util.Formatter.format(Unknown Source)
At java.io.printstream.format(Unknown Source)
At java.io.printstream.printf(Unknown Source)
At Cars.main(Cars.java:27)
Here is my code:
import java.util.Scanner;
public class Cars
{
public static void main(String [] args)
{
Scanner input = new Scanner(System.in);
int carYear, currentYear, carAge;
double costOfCar, salesTaxRate;
double totalCost;
String carModel;
System.out.println("Please enter your favorite car model.");
carModel = input.nextLine();
System.out.println("Please enter the year of the car");
carYear = input.nextInt();
System.out.println("Please enter the current year.");
currentYear = input.nextInt();
carAge = currentYear - carYear;
System.out.println("How much does the car cost?");
costOfCar = input.nextDouble();
System.out.println("What is the sales tax rate?");
salesTaxRate = input.nextDouble();
totalCost = (costOfCar + (costOfCar * salesTaxRate));
System.out.printf("The model of your favorite car is" + carModel + ", the car is" + " " + carAge + " " + " years old, the total of the car is" + " " + "%.2f",totalCost + " " + " dollars.");
}
}
I'm not exactly sure what's causing the issue.

Try:
System.out.printf("The model of your favorite car is %s, the car is %d years old, the total of the car is %.2f dollars.", carModel, carAge, totalCost);
Or the more readable:
System.out.printf("The model of your favorite car is %s," +
" the car is %d years old," +
" the total of the car is %.2f dollars.",
carModel, carAge, totalCost);

It's because %.2f is replaced with the entire second argument in that method call. The problem is that by specifying f in %.2f, you are saying that the second argument is a float or double. The second argument in this case is totalCost + " " + " dollars." which evaluates to a string.
To fix this problem, you need to make the second argument be a float or double. This can be achieved by moving + " " + " dollars." from the end of the second argument to the end of the first argument, like so:
System.out.printf("The model of your favorite car is" + carModel + ", the car is" + " " + carAge + " " + " years old, the total of the car is" + " " + "%.2f" + " " + " dollars.",totalCost);
You can also remove many of the unnecessary concatenations from that line, resulting in this:
System.out.printf("The model of your favorite car is" + carModel + ", the car is " + carAge + " years old, the total of the car is %.2f dollars.", totalCost);

The variable has to go as a parameter to the System.out.printf() function. The "%.2f" will be replaced by the double value that is passed as the second parameter.
For Example:
System.out.printf("The value is %.2f", value);
The same thing is true for other variable types and for multiple variables,
String str = "The value is: ";
double value = .568;
System.out.printf("%s %.2f", str, value);
This will output: "The value is: .57"

Compounding interest program in Java

I'm trying to write this compounding interest program with a do while loop at the end and I cannot figure out how to print out the final amount.
Here is the code I have so far :
public static void main(String[] args) {
double amount;
double rate;
double year;
System.out.println("This program, with user input, computes interest.\n" +
"It allows for multiple computations.\n" +
"User will input initial cost, interest rate and number of years.");
Scanner keyboard = new Scanner(System.in);
System.out.println("What is the initial cost?");
amount = keyboard.nextDouble();
System.out.println("What is the interest rate?");
rate = keyboard.nextDouble();
rate = rate/100;
System.out.println("How many years?");
year = keyboard.nextInt();
for (int x = 1; x < year; x++){
amount = amount * Math.pow(1.0 + rate, year);
}
System.out.println("For " + year + " years an initial " + amount + " cost compounded at a rate of " + rate + " will grow to " + amount);
String go = "n";
do{
System.out.println("Continue Y/N");
go = keyboard.nextLine();
}while (go.equals("Y") || go.equals("y"));
}
}

The trouble is, amount = amount * Math.pow(1.0 + rate, year);. You're overwriting the original amount with the calculated amount. You need a separate value to hold the calculated value while still holding the original value.
So:
double finalAmount = amount * Math.pow(1.0 + rate, year);
Then in your output:
System.out.println("For " + year + " years an initial " + amount +
" cost compounded at a rate of " + rate + " will grow to " + finalAmount);
EDIT: Alternatively, you can save a line, a variable, and just do the calculation inline, as such:
System.out.println("For " + year + " years an initial " + amount +
" cost compounded at a rate of " + rate + " will grow to " +
(amount * Math.pow(1.0 + rate, year)));