Why I can NOT have a class inside a method?

Hi,

I have a method. Inside it, I need a ActionListener. The code is like:

public class DataMgr
{
private JFileChooser chooser = new JFileChooser();

public void saveData()
{
chooser.addActionListener(new SaveFileListener(chooser));
if ( chooser.showSaveDialog(new JPanel()) == JFileChooser.APPROVE_OPTION) //user clicked Save button
...//some code


final class SaveFileListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
...//some code
}
} //end of class SaveFileListener

} //end of method saveData
} //end of class DataMgr

Let me explain my code. I need to save something using JFileChooser to pops up a gui which lets the user to select the path and input file name. Unfortunately, if the user selects an existing file, the program just QUIETLY overwrite it without any warning. So I googled and found that I have to implement my own listener (e.g. SaveFileListener) to achieve such a feature. I am surprised Sun doesn't provide such a feature since it is so obviously needed.

Because the class SaveFileListener is only needed inside the method saveData(), none of other methods need or care its existence, I hope to put the class inside the method scope to make the method self-contained. Then I run into the problem:
first, compiler says that modifier can only be abstract or final. I changed private to final.
Then, compiler says the following line cannot find the type SaveFileListener.
chooser.addActionListener(new SaveFileListener(chooser));

My plan is correct or not? How can I achieve my plan? Thank you very much.

I assume if I put the class SaveFileListener outside the method scope saveData(), things will be fine. But I think that way unrelated code will clutter the programmer's brain.

Thank you very much.
.