Question

Write in Java

Write code which checks validity of a 3-digit positive integer entered by the user.
The number is considered valid (true) if the sum of the first two digits is less than the last.
Otherwise it is invalid (false).

Answer 1

// Java program to check the validity of 3-digit number

public class ThreeDigitValidity {  

   public static void main(String[] args) {
  
       Scanner scan = new Scanner(System.in);
       int num;
       // Input of number
       System.out.print("Enter a 3-digit number: ");
       num = scan.nextInt();
       if(num > 99 && num < 1000) /// check that the number entered is 3-digit
       {
          int temp = num;
           // get the last digit
           int last = temp%10;
           temp = temp/10; // remove the last digit from the number
           int sum = 0;
           // loop to calculate the sum of first 2 digit
           while(temp > 0)
          {
               sum += temp%10;
               temp = temp/10;
           }
         
           // if sum of first 2 digit < last digit, then valid else invalid
           if(sum < last)
               System.out.println(num+" is valid");
          else
               System.out.println(num+" is not valid");
              
}
  }
}
//end of program

Output:

Enter a 3-digit number: 105 105 is valid

Enter a 3-digit number: 234 234 is not valid