I have a program called public class ZeroCounter {. I want to add a new method to it called numberOfDigits() and add a line to test it in the main() method. How should I go abo
Try this.... :)
public class ZeroCounter {
    public static int numberOfDigits(int number) 
    {
        //return Integer.toString(number).length();
        return String.valueOf(number).length();
    }
    public static void main(String[] args)
    {
        int number;
        Scanner Keyboard=new Scanner(System.in);
        System.out.print("Enter the number: ");
        number=Keyboard.nextInt();
        System.out.println("numberOfDigits(" + number + ")=" + numberOfDigits(number));
    }
}
Updated Code..
import java.util.*;
public class ZeroCounter 
{
public static int numberOfDigits(int number,char d) 
{           
    //to get a char array of digits of number
    char[] n=Integer.toString(number).toCharArray();
    int r=0;
    for(char x:n)
    {
        if(x==d)
            r++;
    }
    return r;
}
public static void main(String[] args)
{
    int number;
    char digit;
    boolean flag=false;
    Scanner Keyboard=new Scanner(System.in);
    try{
    System.out.print("Enter the non-negative number: ");
    number=Keyboard.nextInt();
    //to check number is positive or not
    if(number<=-1)
    throw new Exception();
    System.out.println(number + " contains " + numberOfDigits(number,'0') + " zeros.");
    System.out.print("Enter the digit: ");
    //to take only one letter as input
    digit=Keyboard.next(".").charAt(0);
    //to check input is digit or not
    if(!Character.isDigit(digit))
    throw new Exception();
    System.out.println("Number of digits(" + digit + ")=" + numberOfDigits(number,digit));
    }
       //to catch all exceptions
    catch(Exception e)
    {  
        System.out.println("\n You have entered invalid input..");
    }
}
}