Null pointer exception

[izzy]

Basically, my code is like this:

public class Viewer()
{
    private ArrayList<Button> buttonsList;

    private Button button1;

public Viewer()
{
    buttonsList = new ArrayList<Button>();
    addButtons();
}

public void addButtons()
{
    //other code emitted
    button1 = new Button("title");
    if (button1 != null)
    {
        buttonsList.add(button1);  **
    } 
}

It compiles, but I get a run time error saying there's a null pointer exception where I've put the **. I'm not really sure what the problem is, I've initialised button1 and my array list so neither are null, and I've used an if statement so it only adds to array list if button1 is NOT null. i've tried initializing button1 to null, nothing seems to be working.
Any suggestions would be much appreciated!

[PhHein]

Then buttonsList is null. Use Code tags when posting code.

[toadaly]

It's valid to add a null entry to a List, so it really doesn't matter if button1 is null or not. buttonsList is what's null, not button1. My guess is that you are either setting it to null in the ommited code, or redefining a local buttonsList and failing to initialize it.

[Eranga]

Please send the omitted code segment here to look at.

And also please use code tags next time when you post codes here in the forum.

[izzy]

thanks for help, problem has been sorted

[Eranga]

Then please mark the thread solved, from tool menu.