Question

Please write in java: Write a recursive method toNumber that forms the integer sum of all digit characters in a string. For example, the result of toNumber("3ac4") would be 7. Hint: If next is a digit character ('0' through '9'), Character.isDigit(next) is true and the numeric value of next is Character. digit(next, 10).

Answer 1

Java Program :

public class Main
{
    // Recursive function toNumber(s)
    public static int toNumber(String s)
    {
        if(s.isEmpty())          // Base case : return 0 if string is empty
        {
            return 0;
        }
        else                     // string is not empty
        {
            if(Character.isDigit(s.charAt(0))) // check if character is digit from '0' to '9'
            {
                // subract '0' from digit to convert character to integer digit 
                return s.charAt(0) - '0' + toNumber(s.substring(1)); // call the recursive function with remaining string 
            }
            else 
            {
                return toNumber(s.substring(1)); // if not a digit then simply call the recursive function again
            }
        }
    }
        public static void main(String[] args) {
                System.out.println(toNumber("3ac4"));
        }
}

Screenshot :