Re: errors in Hashtable to HashMap

bH <>
Fri, 2 May 2008 16:38:33 -0700 (PDT)
On May 2, 12:58 pm, "Matt Humphrey" <> wrote:

"bH" <> wrote in message
On May 2, 10:33 am, Roedy Green <>

On Fri, 2 May 2008 05:34:40 -0700 (PDT), bH <>
wrote, quoted or indirectly quoted someone who said :

Exception in thread "AWT-EventQueue-2" java.lang.NullPointerException
at TestPhneDialer.action(

Since the listing you post has no line numbers, we can't easily tell
what that is pointing to. Add a comment to point it out.

Roedy Green Canadian Mind Products
The Java Glossary
Hi Matt,
The suggestions that you made do not fix the situation :(

Perhaps you have more than one error. Exactly what did you do and what
error is it producing? Are you sure the browser isn't caching your appl=


You are definately declaring the variable twice.

This is the line 30 that is in error:
String name = new

P.S. I think that this error happens because the buttonSoundNames is
available at this line(not readable at this point in the program).
But that is just my dumb guess.

You know (and can test) that buttonSoundNames is null at this point. No=


work backwards and ask yourself what conditions are needed in order for it=

to be null. Perhaps init() is not called, the initialization is shadowed,
the applet has been cached, etc. Then test each of these hypotheses.

Also, it's not meaningful for the HashMap loadfactor to be > 1.
Essentially, you're saying that when a table of size 3 contains more than =


elements it should be resized.

Matt Humphrey

Hi Matt,

Thanks for your response. Your suggestions are really
appreciated. I have corrected the code so that errors
reported earlier no longer exist.

The major correction happened in the declaration
early in the program.

The following is offered as a solution.

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

@SuppressWarnings( "unchecked" )

public class HMapTestPhneDialer extends Applet {

  boolean DEBUG = false;
  HashMap buttonSoundNames;
  KeyPad keyPad;

  public void init() {
    keyPad = new KeyPad();
    buttonSoundNames = new HashMap<Button,String>();
    // changed this

    buttonSoundNames.put(keyPad.b1, "");
    buttonSoundNames.put(keyPad.b2, "");
    buttonSoundNames.put(keyPad.b3, "");
    setLayout(new FlowLayout());

  public boolean action(Event e, Object arg) {
        if ( instanceof Button) {
            String name =
new String((String)buttonSoundNames.get((Button);
            //results should show "" or"" or ""
            //depending which button press
      return true;
    return false;
class KeyPad extends Panel {
  Button b1,b2,b3;
  KeyPad() {
    b1 = new Button("1");
    b2 = new Button("2");
    b3 = new Button("3");
    setLayout(new GridLayout(4,3,10,10));
Thanks again,


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