练习的代码出错了

第一个文件WriteMail.java代码
import javax.swing.*;
import java.awt.*;

public class WriteMail extends JFrame
{
WriteMailEvent sendmail=new WriteMailEvent(this);

public WriteMail()
{
super("Write an E-mail");
setSize(370,270);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
FlowLayout flow=new FlowLayout(FlowLayout.LEFT);
setLayout(flow);

JPanel row1=new JPanel();
JLabel toLabel=new JLabel("To:");
row1.add(toLabel);
JTextField to=new JTextField(24);
row1.add(to);
add(row1);

JPanel row2=new JPanel();
JLabel subjectLabel=new JLabel("Subject:");
row2.add(subjectLabel);
JTextField subject=new JTextField(24);
row2.add(subject);
add(row2);

JPanel row3=new JPanel();
JLabel messageLabel=new JLabel("Message:");
row3.add(messageLabel);
JTextArea message=new JTextArea(4,22);
message.setLineWrap(true);
message.setWrapStyleWord(true);
JScrollPane scroll=new JScrollPane(message,JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
row3.add(scroll);
add(row3);

JPanel row4=new JPanel();
JButton send=new JButton("Send");
row4.add(send);
add(row4);

send.addActionListener(sendmail);


setVisible(true);

}

public static void main(String[] arguments)
{
WriteMail mail=new WriteMail();
}
}

第二个文件WriteMailEvent.java代码
import javax.swing.*;
import java.awt.event.*;

public class WriteMailEvent implements ItemListener,ActionListener,Runnable
{
WriteMail gui;
Thread Playing;


public WriteMailEvent(WriteMail in)
{
gui=in;
}

public void actionPerformed(ActionEvent event)
{
String command=event.getActionCommand();
if(command=="send") sendPlaying();
}

void sendPlaying()
{Write
Playing=new Thread(this);
Playing.start();
}
}

我想实现的是：当按下send按钮时跳出一个文本框提示你发送成功，确认后退出框架，请问如何编写后续代码呢。

另外我这上面代码有错，说未覆盖监听方法。和WriteMailEvent不是抽象的等等

请高手修改和补充谢谢