59. 下列程序显示了鼠标在窗体拖动时的位置坐标，在下划线处应该填入的代码是______。
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class Test implements MouseMotionListener, MouseListener{
JFrame jf;
JTextField tf;
public static void main(String[] args){
Test test = new Test();
test.go();
}
public void go(){
jf = new JFrame("Test");
tf = new JTextField(30);
jf.add(tf, "South");
jf.setSize(300,200);
jf.addMouseListener(this);
jf.__________(this);
jf.setVisible(true);
}
public void mouseDragged(MouseEvent e){
String s = "Mouse dragging: X="+e.getX()+" Y="+e.getY();
tf.setText(s);
}
public void mouseMoved(MouseEvent e){}
public void mouseClicked(MouseEvent e){}
public void mouseEntered(MouseEvent e){}
public void mouseExited(MouseEvent e){}
public void mouseReleased(MouseEvent e){}
public void mousePressed(MouseEvent e){}
}
