/*
 * This program accepts an input that should be a positive integer
 * and this program validates the input to verify that it is a
 * positive integer.
 */
package validateintegerstrings;
import java.util.Scanner;

/**
 * @author jcmtiernan
 */
public class ValidateIntegerStrings
{
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args)
    {
        String intStrNum;
        int intStr;
        boolean valid = true;        
        Scanner in = new Scanner(System.in);  
        boolean contCheck = true;  // Does the user want to continue?
        
        do
        {
            System.out.print("Please enter a positive integer.  To quit, type capital Q: ");           
            intStrNum = in.next();    
            in.nextLine();
            
            // "Q" will indicate that the user wants to stop running the program
            if (intStrNum.equals("Q"))
            {
                contCheck = false;
            }
            else
            {   /*  The ".matches" method compares the values in the string against \\d+ .
                 *   \\d+ is a regular expression that tests to see if all characters in the 
                 *  string are digits (\\d) and there can be 1 or more digits (+)   
                 */
                valid = intStrNum.matches("\\d+");

                if (valid)
                {    // This turns the digits of string intStrNum into an int
                    int length = intStrNum.length();
                    intStr = Integer.parseInt(intStrNum.substring(0,length));  
                    System.out.printf("You entered %d which is a positive integer. \n\n",intStr);             
                }  
                else
                {
                    System.out.printf("You entered %s which is NOT a positive integer. \n\n",intStrNum);  
                }     
            }
        }
        while(contCheck);
    }
    
}