这段程序为什么在JBuilder可以运行，在DOS下编译不可以呢。

import java.awt.*;
import java.awt.event.*;
public class Button
{
    public static void main(String args[])
    {
        MyButton but=new MyButton("窗口");
    }
}
class MyButton extends Frame implements ActionListener
{
    Button button1,button2,button3;
    MyButton(String s)
    {
        this.setTitle("Button");
        setLayout(new FlowLayout());
        button1=new Button("红色");
        button2=new Button("绿色");
        button3=new Button("黄色");
        add(button1);
        add(button2);
        add(button3);
        button1.addActionListener(this);
        button2.addActionListener(this);
        button3.addActionListener(this);
        setBounds(100,100,300,200);
        setVisible(true);
        validate();
    }
    public void actionPerformed(ActionEvent e)
    {
        if(e.getSource()==button1)
        {
            this.setBackground(Color.red);
        }
        if(e.getSource()==button2)
        {
            this.setBackground(Color.green);
        }
        if(e.getSource()==button3)
        {
            this.setBackground(Color.yellow);
        }
    }
}