JFileChooser inside applet

gistfile1.java

import java.util.ArrayList;
import javax.swing.SwingWorker;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.JFileChooser;
import netscape.javascript.*;

public class myApplet extends JApplet {
	private ArrayList<String> imageList = new ArrayList<>();
	
	private void finish() {
        	JSObject window = null;
        	try {
			window = JSObject.getWindow(this);
        		String results = null;
        		if (imageList.size() > 0) { Arrays.toString(imageList.toArray()) };

        		if (results != null) {
            			window.eval("appletCallback(" + results + ")");
        		} else {
            			window.eval("appletCallback()");
        		}
        	} catch (Exception ex) {
			//do nothing
        	}
    	}

  	@Override
    	public void init() {
        	try {
            		//set display prefs
            		setSize(640, 480);
            		UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());

            		//initialize form components
            		java.awt.EventQueue.invokeAndWait(new Runnable() {
                		public void run() {
                    			initComponents();
                		}
            		});
		} catch (Exception e) {
            		//e.printStackTrace();
       		}
	}

	@SuppressWarnings("unchecked")
	private void initComponents() {
		jPanel9 = new javax.swing.JPanel();
        	btnScan = new javax.swing.JButton();
        	btnAttach = new javax.swing.JButton();

		btnAttach.setText("Attach");
        	btnAttach.setToolTipText("Attach image(s)");
        	btnAttach.addActionListener(new java.awt.event.ActionListener() {
           		public void actionPerformed(java.awt.event.ActionEvent evt) {
                		btnAttachActionPerformed(evt);
            		}
        	});
        	jPanel9.add(btnAttach);
	}

	private void btnAttachActionPerformed(java.awt.event.ActionEvent evt) {                                          
        	LoadData loader = new LoadData();
        	loader.addPropertyChangeListener(this);
        	loader.execute();
    	}
	
	private class LoadData extends SwingWorker<Void, Void> {
        	@Override
        	protected Void doInBackground() throws Exception {
	            	String filePath = prefs.get("filepath", "");
	        	JFileChooser chooser = new JFileChooser(filePath);
			File selection[];
			String imgFile = "";

			chooser.setCurrentDirectory(lastPath);
	            	chooser.setFileFilter(filter);
	            	chooser.setMultiSelectionEnabled(true);
	
			if (chooser.showOpenDialog(rootPane) == JFileChooser.APPROVE_OPTION) {
				selection = chooser.getSelectedFiles();
				for (int i = 0; i < selection.length; i++) {
	                        	imageList.add(selection[i].getPath());
				}
				finish();
			}
		}
	}
}