New to Java

Hi all,
regarding the first part where pass of string array into object array. I have done it (thanks again for the help). But regarding the add and remove elements from the Jlist cant be done.. below is my code for the delete button when press. I cast it into int for the ManualList.getSelectedIndex();(at part A) but cant display and keep having a error call
java.lang.NullPointerException at ManualChange&ValueReporter.valueChanged
code for value reporter is at part B

Part A
private void deleteMouseClicked(MouseEvent e)
{
int n =(int)ManualList.getSelectedIndex();
if (!(n < 0) || (n > listModel.size()))
{
listModel.remove(n);
}
delete.setEnabled(false);
ManualList.repaint();
ManualList.revalidate();
}

Part B

private class ValueReporter implements ListSelectionListener {
public void valueChanged(ListSelectionEvent event) {
// if (!event.getValueIsAdjusting())
// gettext.setText(ManualList.getSelectedValue().toString());
ManualList.repaint();
ManualList.revalidate();

}

Any help is greatly appreciated.



alright, i redo part A the code is shown below but i still cant get the display out.
Is there some problem in my code? or is the repaint and revalidate thing wrong usage here ? Need help regarding this. Thanks


int n =ManualList.getSelectedIndex();
if (!(n < 0) || (n > listModel.size()))
{
listModel.removeElement(arrayObject[n]);
}
delete.setEnabled(false);
ManualList.repaint();
ManualList.revalidate();