Re: Why I can NOT have a class inside a method?

Knute Johnson <>
Thu, 28 Sep 2006 10:59:57 -0700
Shawn wrote:


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

public class DataMgr

Should be class SaveFileListener extends ActionListener or
ActionListener saveFileListener = new ActionListener() {
in any case it must be defined before you use it in your code

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

    } //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
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.


Knute Johnson
email s/nospam/knute/

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