Core Design Patterns: Command Pattern

Command Pattern: Actionları objeye encapsule etme yönteminin adıdır. Her bir action bir object olarak düşünülür. Bu sayede yeniden kullanabilme, loglayabilme, undo v.s. bir çok vantaj sağlamaktadır.

Örnek Kod:
/*
The Design Patterns Java Companion

Copyright (C) 1998, by James W. Cooper

IBM Thomas J. Watson Research Center

*/

package CommandPattern;

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;

public class ActionCommand extends Frame {
Menu mnuFile;

MenuItem mnuOpen, mnuExit;

Button btnRed;

Panel p;

Frame fr;

//-----------------------------------------
public ActionCommand() {
super("Frame without commands");
fr = this; //sae cop of this frame
MenuBar mbar = new MenuBar();
setMenuBar(mbar);

mnuFile = new Menu("File", true);
mbar.add(mnuFile);

mnuOpen = new MenuItem("Open...");
mnuFile.add(mnuOpen);
mnuExit = new MenuItem("Exit");
mnuFile.add(mnuExit);

mnuOpen.addActionListener(new fileOpen());
mnuExit.addActionListener(new fileExit());

btnRed = new Button("Red");
p = new Panel();
add(p);
p.add(btnRed);

btnRed.addActionListener(new btnRed());
setBounds(100, 100, 200, 100);
setVisible(true);
}

//-----------------------------------------
private void exitClicked() {
System.exit(0);
}

//-----------------------------------------
static public void main(String argv[]) {
new ActionCommand();
}

//=====----====--inner classes---=====----
class fileOpen implements ActionListener {
public void actionPerformed(ActionEvent e) {
FileDialog fDlg = new FileDialog(fr, "Open a file", FileDialog.LOAD);
fDlg.show();
}
}

//-------------------------------------
class btnRed implements ActionListener {
public void actionPerformed(ActionEvent e) {
p.setBackground(Color.red);
}
}

//-------------------------------------
class fileExit implements ActionListener {
public void actionPerformed(ActionEvent e) {
System.exit(0);
}
}
}
//=====================================