Trouble with isDigit method

Question

Hi guys,
I am currently in the middle of my first Assignment for an intro to java. I seem to have done alright so far, except just for a couple of minor details. Firstly, I am developing an EXTREMELY basic atm prototype. I am passing the staring balance as a HTML parameter. I wan't to check that is is all numeric. If not then I want the label that displays the updated balance to say something like "must enter valid dollar amount". I know I have to use the isDigit method, 'cause I have successfully done that for my textfield, but I have absolutely no idea how to do it for this. I shall paste the relevant sections of code (that apear in order) and hope someone can help :)
public void init()
     {//start of init method - initialisation of the applet
          //assigning inital balance to current balance variable
          StartBalStr = this.getParameter("InitialBalParameter");
          if ((StartBalStr == null) || (StartBalStr.equals("")))
               StartBalStr = "No Starting Balance Provided";
public static boolean isStringAllNumeric(String aString)
     {//looping structure to check from the first character to the last of the value entered
          int stringSize = aString.length();
          for (int i = 0; i < stringSize; i++)
               boolean check = Character.isDigit(aString.charAt(i));
               if (!check)
               return false;//if any characters at each position of the string's length is not a digit
                    return true;//if any characters at each position of the string's length is a digit
     }//end of isStringAllNumeric function     
public void keyTyped(KeyEvent ke)
               char c = ke.getKeyChar();
               if (!((Character.isDigit(c)) || (c == KeyEvent.VK_BACK_SPACE) || (c == KeyEvent.VK_DELETE) || (c == '.')))
                    getToolkit().beep();
                    ke.consume();

Answer 1

How about this....
if (isStringAllNumeric(StartBalStr)) {
System.out.println("The param is numeric");
} else {
System.out.println("The param is non-numeric");
Hope that was what you were after.
Alan