import java.awt.*;
import java.awt.event.*;

public class test1
{
    public static void main(String[] args)
    {
        new create();   
    }
}

class create implements ActionListener
{
    Button btn;
   
    create()
    {
        btn=new Button("test");
       
        add(btn);//显示说这里有错误…
       
        btn.addActionListener(this);
    }
   
    public void actionPerformed(ActionEvent e)
    {
        if(btn.getLabel().equals("test"))
        {
            btn.setLabel("After");
        }
        else
        {
            btn.setLabel("test");
        }
    }
}

btn=new Button("test");
        btn.addActionListener(this);
        this.add(btn);

       这样试试
      

import java.awt.*;
import java.awt.event.*;

public class Test1
{
    public static void main(String[] args)
    {
        new Create();   
    }
}

class Create extends Frame implements ActionListener
{
    Button btn;
   
    Create()
    {
        btn=new Button("test");
      
        add(btn);
      
        btn.addActionListener(this);
    pack();
    setVisible(true);
    }
   
    public void actionPerformed(ActionEvent e)
    {
        if(btn.getLabel().equals("test"))
        {
            btn.setLabel("After");
        }
        else
        {
            btn.setLabel("test");
        }
    }
}

这样就行了!!