Thread: converting words to numbers like a phone. i.e. 1800CALLMEE = 1-800-225-5544

Please Help! I can't get this program to run correctly...
I have 2 questions so far:

1.) How do i get my program to print each number instead of just the very last number? I was thinking maybe it had something to do with the break;'s. this is the first time i've ever used a switch statement.

2.) Why do I keep getting a "NullPointerException" error? it says "java.lang.NullPointerException
at PhoneClientDialog.main(PhoneClientDialog.java:10)"

Here's my student class code:

public class Phone
{
    private String word;
    private String number;
 
    public Phone(String word)
    {
        this.word = word;
        this.setNumber();
    }
 
    private void setNumber()
    {
       //Assign number to empty string to avoid null. 
       this.number = ("");
 
       //Convert characters in word to digits.
       int index = 0;
 
       while (index < this.word.length())
       {   
               //Places digits in number.
               switch(this.word.toLowerCase().charAt(index))
               {
                       //#2
                       case 'a': this.number = "2"; break;
                       case 'b': this.number = "2"; break;
                       case 'c': this.number = "2"; break;
                       //#3
                       case 'd': this.number = "3"; break;
                       case 'e': this.number = "3"; break;
                       case 'f': this.number = "3"; break; 
                       //#4
                       case 'g': this.number = "4"; break;
                       case 'h': this.number = "4"; break;
                       case 'i': this.number = "4"; break;
                       //#5
                       case 'j': this.number = "5"; break;
                       case 'k': this.number = "5"; break;
                       case 'l': this.number = "5"; break;
                       //#6
                       case 'm': this.number = "6"; break;
                       case 'n': this.number = "6"; break;
                       case 'o': this.number = "6"; break;
                       //#7
                       case 'p': this.number = "7"; break;
                       case 'r': this.number = "7"; break;
                       case 's': this.number = "7"; break;
                       //#8
                       case 't': this.number = "8"; break;
                       case 'u': this.number = "8"; break;
                       case 'v': this.number = "8"; break;
                       //#9
                       case 'w': this.number = "9"; break;
                       case 'x': this.number = "9"; break;
                       case 'y': this.number = "9"; break;
               }
         index++;
       }        
    }
 
    //public method that returns number.
    public String toString()
    {
        return this.number;
    }
 
 
}

and here is my parent class code:

import javax.swing.JOptionPane;
 
public class PhoneClientDialog
{
   public static void main(String[] args)
   {
      String input = JOptionPane.showInputDialog(
         "Complete the phone number with a word (quit terminates program): 1-800-");
 
	  while(!(input.equalsIgnoreCase("quit")))
	  {
		  Phone myPhone = new Phone(input);
		  input = JOptionPane.showInputDialog("The actual phone number is 1-800-" + myPhone + '\n' +
         	"Complete the phone number with a word (quit terminates program): 1-800-");
	  }
 
      System.exit(0);
   }
}

the parent class is the one throwing codes but my professor wrote it and we're not allowed to touch it. i would e-mail him but it's the weekend. :/