菜鸟求助点击按钮显示文字

求助为什么显示不出来哦   import java.io.IOException;
   import java.net.DatagramPacket;
   import java.net.DatagramSocket;
   import java.net.InetAddress;
   import java.net.SocketException;
   import java.awt.BorderLayout;//边框布局
   import java.awt.event.ActionEvent;
   import java.awt.event.ActionListener;
   import javax.swing.*;
   import javax.swing.JFrame;
   import javax.swing.JScrollPane;//提供常用面板  http://www.jingningedu.com/manage/java_api/javax/swing/JScrollPane.html
   import javax.swing.JTextArea;
   import javax.swing.JTextField;
   import javax.swing.SwingUtilities;
   import java.awt.event.*;
   
public class runsmalltalk extends JFrame
{
private JTextField enterField;
private JTextArea displayArea;
private JButton b1=new JButton("点击发送消息");
private DatagramSocket socket; public runsmalltalk()
{
super("runsmalltalk");
enterField=new JTextField("");///////public, private, protected这种东西，不能写在方法里面 要写在class内，method外
displayArea=new JTextArea();
setLayout(null);
add(enterField);
enterField.setBounds(0,0,400,30);
add(b1);

b1.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent event)
{
displayArea.append("clickedfdsgsfsdffffffffffffffffffffffffffffffffffffffffffffff");
}
});
b1.setBounds(0,30,400,20);

JScrollPane aa=new JScrollPane(displayArea);
aa.setBounds(0,50,400,350);
setSize( 400, 300 ); // set window size
          setVisible( true ); // show window显示
         
}

}