与病人交谈时，“沉默”宜用于()。

A．交谈开始时

B．交谈结束时

C．交谈过程中

D．自始至终

E．开始与结束时

本题的功能是监听鼠标的拖曳操作。窗口中有一个列表框，列表框中列出了当前目录的所有文件，鼠标选中一个或多个文件后拖曳出窗口，此操作的功能是将拖曳的文件复制一份在拖曳的目的目录下。
import java.awt.*;
import java.awt.datatransfer.*;
import java.awt.dnd.*;
import java.awt.event.*;
import java.io.*;
import java.util.*;
import javax.swing.*;
public class java3

public static void main(String[]args)

JFrame frame=new DragSourceFrame();
frame.setDefauhCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.show();


class DragSourceFrame extends JFrame

public DragSourceFrame()

setTitle("java3");
setSize(WIDTH,HEIGHT);
Container contentPane=getContentPane();
File f=new File(".").getabsoluteFile();
File[]files=f.listFiles();
model=new DefauhListModel();
for(int i=0;i＜files.length();i++)
try

model.addElement(files[i].getCanonicalFile());

catch(IOException exception)

JOptionPane.showMessageDialog(this,exception);

fileList=new JList(model);
contentPane.add(new JScrollPane(fileList),
BorderLayout.CENTER);
contentPane.add(new JLabel("从列表中拖曳出文件"),
BorderLayout.NORTH);
DragSource dragSource=DragSource.getDefaultDragSource();
dragSource.createDefaultDragGestureRecognizer(ileList,
DnDConstants.ACTION_COPY_OR_MOVE,new
DragGestureListener()

public void dragGestureRecognized(
DragGestureEvent event)

draggedValues=fileList.getSelectedValues();
Transferable transferable
=new FileListTransferable(draggedValues);
event,startDrag(null,transferable,
new FileListDragSourceListener());

);

private class FileListDragSourceListener implements DragSourceAdapter

public void dragDropEnd(DragSourceDropEvent event)

if(event.getDropSuccess())

int action=event.getDropAction();
if(action==DnDConstants.ACTION_MOVE)

for(int i=0;i＜draggedValues.length i++)
model.removeElement(draggedValues[i]);




private JList fileList;
private DefaultListModel model;
private Object[]draggedValues;
private static final int WIDTH=300;
private static final int HEIGHT=200;

class FileListTransferable implements Transferable

public FileListTransferable(Object[]files)

fileList=new ArrayList(Arrays.asList(files));

public DataFlavor[]getTransferDataFlavors()

return flavors;

public boolean isDataFlavorSupported(DataFlavor flavor)

return Arrays.asList(flavors).contains(flavor);

public Object getTransferData(DataFlavor flavor)
throws UnsupportedFlavorException

if(flavor.equals(DataFlavor.javaFileListFlavor))
return fileList;
else if(flavor.equals(DataFlavor.stringFlavor))
return fileList.toString();
else
throw new UnsupportedFlavorException(flavor);

private static DataFlavor[]flavors=

DataFlavor.javaFileListFlavor,
DataFlavor.stringFlavor
;
private java.util.List fileList;