java gui 选择文件

import java.io.File;
import java.io.IOException;
import java.util.Scanner;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JTextArea;
public class DisplayFile {
       /**
        * @param args
        */
       public static void main(String[] args)throws IOException {
              // TODO Auto-generated method stub
              JFrame frame =new JFrame("Display File");
              frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
              JTextArea ta=new JTextArea(20,30);
              JFileChooser chooser=new JFileChooser();
              int status =chooser.showOpenDialog(null);
              if(status!=JFileChooser.APPROVE_OPTION)
                     ta.setText("No file chosen!");
              else
              {
                     File file=chooser.getSelectedFile();
                     Scanner scan=new Scanner(file);
            &nb