Command模式例子3

import java.awt.Button;   
import java.awt.Color;   
import java.awt.FileDialog;   
import java.awt.Frame;   
import java.awt.Menu;   
import java.awt.MenuBar;   
import java.awt.MenuItem;   
import java.awt.Panel;   
import java.awt.event.ActionEvent;   
import java.awt.event.ActionListener;   
  
interface Command {   
  public void Execute();   
}   
  
public class ExtrnCommand extends Frame implements ActionListener {   
  Menu mnuFile;   
  
  fileOpenCommand mnuOpen;   
  
  fileExitCommand mnuExit;   
  
  btnRedCommand btnRed;   
  
  Panel p;   
  
  Frame fr;   
  
  //-----------------------------------------   
  public ExtrnCommand() {   
    super("Frame with external commands");   
    fr = this; //save frame object   
    MenuBar mbar = new MenuBar();   
    setMenuBar(mbar);   
  
    mnuFile = new Menu("File", true);   
    mbar.add(mnuFile);   
  
    mnuOpen = new fileOpenCommand("Open...", this);   
    mnuFile.add(mnuOpen);   
    mnuExit = new fileExitCommand("Exit");   
    mnuFile.add(mnuExit);   
  
    mnuOpen.addActionListener(this);   
    mnuExit.addActionListener(this);   
  
    p = new Panel();   
    add(p);   
    btnRed = new btnRedCommand("Red", p);   
  
    p.add(btnRed);   
  
    btnRed.addActionListener(this);   
    setBounds(100, 100, 200, 100);   
    setVisible(true);   
  }   
  
  //-----------------------------------------   
  public void actionPerformed(ActionEvent e) {   
    Command obj = (Command) e.getSource();   
    obj.Execute();   
  }   
  
  //-----------------------------------------   
  static public void main(String argv[]) {   
    new ExtrnCommand();   
  }   
}   
//==========================================   
  
class btnRedCommand extends Button implements Command {   
  Panel p;   
  
  public btnRedCommand(String caption, Panel pnl) {   
    super(caption);   
    p = pnl;   
  }   
  
  public void Execute() {   
    p.setBackground(Color.red);   
  }   
}   
//------------------------------------------   
  
class fileOpenCommand extends MenuItem implements Command {   
  Frame fr;   
  
  public fileOpenCommand(String caption, Frame frm) {   
    super(caption);   
    fr = frm;   
  }   
  
  public void Execute() {   
    FileDialog fDlg = new FileDialog(fr, "Open file");   
    fDlg.show();   
  }   
}   
//-------------------------------------------   
  
class fileExitCommand extends MenuItem implements Command {   
  public fileExitCommand(String caption) {   
    super(caption);   
  }   
  
  public void Execute() {   
    System.exit(0);   
  }   
}