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"Java@Work"
by Al Williams
Web Techniques, November 1998

Web Techniques grants permission to use these listings (and code) for 
private or commercial use provided that credit to Web Techniques and 
the author is maintained within the comments of the source. For 
questions, contact editors@web-techniques.com. 



[LISTING ONE]


// Telnumapp.java
// Telephone number applet -Williams
// Simple applet to convert a 
// phone number into a string

import java.util.*;
import java.applet.*;
import java.awt.*;

public class Telnumapp extends Applet
  {
  // UI parts
  TextField num;  
  Button go;
  List list;

// Old-style event handler for the button
// Obviously, just for applet
 public  boolean action(Event evt, Object what)
  {
   if (evt.target==go)
     {
           Vector vec;
           Enumeration e;
           int i;
           String s;
           s=num.getText();
           int nums[]=new int[s.length()];
           // create integer input array
           for (i=0;i<s.length();i++)
           nums[i]=Integer.parseInt(s.substring(i,i+1));
// process it
           vec=process(nums);
// display results
           e=vec.elements();
           list.removeAll();
           while (e.hasMoreElements())
           list.addItem((String)e.nextElement());
           return true;
     
     }
  return false;
  }

// Initialize applet (applet only)
  public void init()
  {
  setLayout(new BorderLayout());
  num=new TextField();
  list=new List();
  go=new Button("Process");
  add(num,"North");
  add(go,"Center");
  add(list,"South");
  show();
  }


// This begins the non-applet portion of the code
// The process routine is common to both applet and
// non-applet

// Translation array
  static String ary[][]=
    {
      {"0","0","0"},
      {"1","1","1"},
      {"A","B","C"},
      {"D","E","F"},
      {"G","H","I"},
      {"J","K","L"},
      {"M","N","O"},
      {"P","R","S"},
      {"T","U","V"},
      {"W","X","Y"}
    };

// This function actually processes a phone number
// (in integer array form) into a vector of
// strings
static Vector process(int []iary)
  {
  int[] idx=new int[iary.length];
  String result;
  Vector rv=new Vector();
  mainloop:
  while (true)
    {
    boolean carry=true;
// Construct a new name
    result=new String();
    for (int q=0;q<iary.length;q++)
     result=result+ary[iary[q]][idx[q]];
// Add it to the list of returned names
   rv.addElement(result);
// Add 1 to iary using base 3 carry semantics 
   for (int i=iary.length-1;i>=0&&carry;i--)
     {
// but not for 0 or 1, skip those
     if (ary[iary[i]][0].equals("0")||ary[iary[i]][0].equals("1"))
       {
       carry=true;
       continue;  // only do "0" and "1" one time each
       }
     idx[i]=idx[i]+1;  // add 1 to the current digit
     if (idx[i]==3)    // overflow?
       {
	 if (i==0) break mainloop;  // done!
         idx[i]=0;
         carry=true;
       }
     else
       {
       carry=false;
       }
     }
    }
  return rv;
  }

// main program - not used when we are an applet
public static void main(String argv[])
  {
  int i;
  Vector v;
  Enumeration e;
  String s;
  int nums[]=new int[argv[0].length()];
// build input array
  for (i=0;i<argv[0].length();i++)
    nums[i]=Integer.parseInt(argv[0].substring(i,i+1));
// do processing 
  v=process(nums);
// print elements
  e=v.elements();
  while (e.hasMoreElements()) System.out.println(e.nextElement());
  }
}