That is definately not what you want. Look at the File class, it's listFiles() method, design an icon for each "filetype", add an actionlistener to this "button", and with that actionlistener, open a JDialog. On that JDialog place the icons.
There is not a "one-click" solution to this, unless you use JFileChooser. That is the only "folder displayer" in the Swing arsenal that I am aware of. Any other view you will have to do yourself.