java 实现拖动文件到窗口功能

package tuo;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.datatransfer.DataFlavor;
import java.awt.dnd.DnDConstants;
import java.awt.dnd.DropTarget;
import java.awt.dnd.DropTargetAdapter;
import java.awt.dnd.DropTargetDropEvent;
import java.io.File;
import java.util.List;

import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class tuo extends JFrame{

    JPanel jp1;
    public tuo()
     {

        jp1 =new JPanel();
        jp1.setBackground(Color.yellow);
        getContentPane().add(jp1,BorderLayout.CENTER);
        setSize(500,200);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocation(400,200);
        setTitle("tuozhuai");
        drag();

     }

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        try {
            UIManager.setLookAndFeel("com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel");
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (InstantiationException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (UnsupportedLookAndFeelException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        new tuo().setVisible(true);

    }

    public void drag()
     {
        new DropTarget(jp1,DnDConstants.ACTION_COPY_OR_MOVE,new DropTargetAdapter()
         {
            @Override
            public void drop(DropTargetDropEvent dtde)
            {
                try{

                    if(dtde.isDataFlavorSupported(DataFlavor.javaFileListFlavor))
                     {
                        dtde.acceptDrop(DnDConstants.ACTION_COPY_OR_MOVE);
                        List<File>list=(List<File>)(dtde.getTransferable().getTransferData(DataFlavor.javaFileListFlavor));

                        String temp="";
                        for(File file:list)
                         {
                            temp+=file.getAbsolutePath()+";\n";
                            JOptionPane.showMessageDialog(null, temp);
                            dtde.dropComplete(true);

                         }

                     }

                    else
                     {

                        dtde.rejectDrop();
                     }

                }catch(Exception e){e.printStackTrace();}

            }

         });

     }

}