Java Swing : Updating screen to show new listbox contents

Hi. This is a newbie question.
I have a simple Java program with Swing. An extract:

listData = new Vector();
listData.add("Hello there");
listData.add("hihi");
listbox1 = new JList( listData );
...
midSection.add(listbox1, BorderLayout.CENTER);

This works, and it displays the contents of the vector in the Listbox on the screen just fine.

The problem is when a button is pressed, the listData vector gets modified. How can I make the listbox "update" to show the new contents?

Thanks

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