swing拖拽时加入按键该如何处理

从JTREE拖拽到JTextArea
如果我用鼠标直接拖拽JTREE的节点到JTextArea那么在JTextArea只显示JTREE节点的NAME
如果我按住ALT再用鼠标拖拽JTREE的节点到JTextArea那么在JTextArea显示固定的String请问按住ALT键这个事件该怎么处理=。=下面的代码现实了第一个假设：
package swing;import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.awt.datatransfer.UnsupportedFlavorException;
import java.awt.dnd.DnDConstants;
import java.awt.dnd.DragGestureEvent;
import java.awt.dnd.DragGestureListener;
import java.awt.dnd.DragSource;
import java.awt.dnd.DragSourceContext;
import java.awt.dnd.DragSourceDragEvent;
import java.awt.dnd.DragSourceDropEvent;
import java.awt.dnd.DragSourceEvent;
import java.awt.dnd.DragSourceListener;
import java.awt.dnd.DropTarget;
import java.awt.dnd.DropTargetDragEvent;
import java.awt.dnd.DropTargetDropEvent;
import java.awt.dnd.DropTargetEvent;
import java.awt.dnd.DropTargetListener;
import java.io.IOException;import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.TreePath;public class DragAndDrop extends JFrame {
    JScrollPane jScrollPane1 = new JScrollPane();
    JTextArea jTextArea1 = new JTextArea();    public DragAndDrop() {
        try {
            jbInit();
        } catch (Exception exception) {
            exception.printStackTrace();
        }
//        getContentPane().setLayout(BorderLayout.CENTER);
        jScrollPane1.getViewport().setBackground(new Color(105, 38, 125));
        jTextArea1.setBackground(Color.orange);
        jTextArea1.setToolTipText("");
        JTree jtr = new JTree();
        jtr.setBackground(Color.BLUE);
        jScrollPane1.getViewport().add(jtr);
        this.getContentPane().add(jTextArea1,
         BorderLayout.NORTH);
        this.getContentPane().add(jScrollPane1,
         BorderLayout.CENTER);        DragSource dragSource = DragSource.getDefaultDragSource(); //创建拖拽源
        dragSource.createDefaultDragGestureRecognizer(jtr,
                DnDConstants.ACTION_COPY_OR_MOVE,
                new DragAndDropDragGestureListener()); //建立拖拽源和事件的联系
      DropTarget dropTarget = new DropTarget(jTextArea1,
            new DragAndDropDropTargetListener());    }    private void jbInit() throws Exception {    }    public static void main(String[] args) {        DragAndDrop dad = new DragAndDrop();
        dad.setTitle("拖拽演示");
        dad.setSize(400, 300);
        dad.setVisible(true);    }
}
class DragAndDropDragGestureListener implements DragGestureListener {
    public void dragGestureRecognized(DragGestureEvent dge) {
        //将数据存储到Transferable中，然后通知组件开始调用startDrag()初始化
        JTree tree = (JTree) dge.getComponent();
      TreePath path = tree.getSelectionPath();
       if(path!=null){
           DefaultMutableTreeNode selection = (DefaultMutableTreeNode) path
            .getLastPathComponent();
           DragAndDropTransferable dragAndDropTransferable = new
                   DragAndDropTransferable(selection);
           dge.startDrag(DragSource.DefaultCopyDrop, dragAndDropTransferable, new DragAndDropDragSourceListener());
       }
    }
}
class DragAndDropTransferable implements Transferable {
    private DefaultMutableTreeNode treeNode;
    DragAndDropTransferable(DefaultMutableTreeNode treeNode) {
        this.treeNode = treeNode;
    }
    static DataFlavor flavors[] = {DataFlavor.stringFlavor};
    public DataFlavor[] getTransferDataFlavors() {
        return flavors;
    }    public boolean isDataFlavorSupported(DataFlavor flavor) {
        if(treeNode.getChildCount()==0){
         return true;
        }
        return false;
    }    public Object getTransferData(DataFlavor flavor) throws
            UnsupportedFlavorException, IOException {      return treeNode;
   
    }
}
 class DragAndDropDragSourceListener implements DragSourceListener {
  public void dragDropEnd(DragSourceDropEvent dragSourceDropEvent) {
    if (dragSourceDropEvent.getDropSuccess()) {
        //拖拽动作结束的时候打印出移动节点的字符串
      int dropAction = dragSourceDropEvent.getDropAction();
      if (dropAction == DnDConstants.ACTION_MOVE) {
        System.out.println("MOVE: remove node");
      }
    }
  }  public void dragEnter(DragSourceDragEvent dragSourceDragEvent) {
    DragSourceContext context = dragSourceDragEvent
        .getDragSourceContext();
    int dropAction = dragSourceDragEvent.getDropAction();
    if ((dropAction & DnDConstants.ACTION_COPY) != 0) {
      context.setCursor(DragSource.DefaultCopyDrop);
    } else if ((dropAction & DnDConstants.ACTION_MOVE) != 0) {
      context.setCursor(DragSource.DefaultMoveDrop);
    } else {
      context.setCursor(DragSource.DefaultCopyNoDrop);
    }
  }  public void dragExit(DragSourceEvent dragSourceEvent) {
  }  public void dragOver(DragSourceDragEvent dragSourceDragEvent) {
  }  public void dropActionChanged(DragSourceDragEvent dragSourceDragEvent) {
  }
}
class DragAndDropDropTargetListener implements DropTargetListener{
    public void dragEnter(DropTargetDragEvent dtde){
   
    }
    public void dragOver(DropTargetDragEvent dtde){
    }
    public void dropActionChanged(DropTargetDragEvent dtde){
    }
    public void dragExit(DropTargetEvent dte){
    }
    public void drop(DropTargetDropEvent dtde){
       Transferable tr=dtde.getTransferable();//使用该函数从Transferable对象中获取有用的数据
       String s="";
        try {
            if(tr.isDataFlavorSupported(DataFlavor.stringFlavor)){
                s = tr.getTransferData(DataFlavor.stringFlavor).toString();
//                s = "helloword";
            }
        } 
        //catch (IOException ex) {
        // } catch (UnsupportedFlavorException ex) {
        // }
        catch(Exception e){
        
        }
        System.out.println(s);
        DropTarget c=(DropTarget)dtde.getSource();
        JTextArea d=(JTextArea)c.getComponent();
        if(s!=null&&s!=""){
            d.append(s + "\n");
        }
    }
}