Как исправить ошибки в коде Jàva?

import javax.swing.*;
import java.awt.*;
public class SimpleGui implements ActionListener
{
JFrame frame;
public static void main (String[ ] ags)
{
SimpleGui gui = new SimleGui();
gui.go(); //error
}
public void go()
{
frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JButton button = new JButton ("Change colors");
button.addActionListener(this );
MyDrawPanel drawPanel = new MyDrawPanel();
frame.getContentPanel().add(BorderLayout.SOUTH, button);
frame.getContentPanel().add(BorderLayout.CENTER, drawPanel); //error
frame.setSize(300, 300);
frame.setVisible(true);
}
public void actionPerformed(ActionEvent event)
{
frame.repaint(); }
}