命令模式封裝調用一個例子publicvoidactionPerformed(ActionEvente){ Objectobj=e.getSource(); if(obj==mnuOpen)fileOpen();//openfile if(obj==mnuExit)exitClicked();//exitfromprogram if(obj==btnRed)redClicked();//turnred}privatevoidexitClicked(){System.exit(0);}privatevoidfileOpen(){ FileDialogfDlg=newFileDialog(this,"Openafile",FileDialog.LOAD); fDlg.show();}privatevoidredClicked(){ p.setBackground(Color.red);}上述程序設計，當按鈕和菜單項不多的時候工作良好，但按鈕和菜單項多時，就不好辦了。publicinterfaceCommand{ publicvoidExecute();}publicvoidactionPerformed(ActionEvente){ Commandcmd=(Command)e.getSource(); cmd.Execute();}這樣，我們需要給每一個對象提供一個執行的方法。命令模式theseprogramobjectsshouldbecompletelyseparatefromeachotherandshouldnothavetoknowhowotherobjectswork.TheuserinterfacereceivesacommandandtellsaCommandobjecttocarryoutwhateverdutiesithasbeeninstructedtodo.TheUIdoesnotandshouldnotneedtoknowwhattaskswillbeexecuted.命令模式程序對象應該徹底的彼此解耦，不需要知道其他的對象是如何工作的。用戶界面接收到命令然后告訴命令對象執行設定的工作，用戶界面不知道也不應該知道命令是如何執行的。命令的發送者命令的接受者命令對象解耦了命令的發送者和命令的接受者飯店用餐顧客點了飯菜，形成一個訂單，侍者將訂單交給廚房，廚房根據訂單配菜。侍者無需知道訂單的內容。飯菜的制作者和飯菜的消費者完全分開，彼此無需直接聯系。遙控器的例子遙控器需要控制每一個電器的動作，如電燈，電扇，電視機，同是開，動作不一樣。我們設置命令接口

publicinterfaceCommand{publicvoidexecute();}publicclassLightOnCommandimplementsCommand{ Lightlight; publicLightOnCommand(Lightlight){ this.light=light; } publicvoidexecute(){ light.on(); }}命令的接收對象命令接收對象自己執行命令對象接收對象實現了命令接口execute（）{receive.action();}

接受者CommandpublicclassSimpleRemoteControl{ Commandslot; publicSimpleRemoteControl(){}

publicvoidsetCommand(Commandcommand){ slot=command; }publicvoidbuttonWasPressed(){ slot.execute(); }}遙控器測試publicclassRemoteControlTest{ publicstaticvoidmain(String[]args){ SimpleRemoteControlremote=newSimpleRemoteControl(); Lightlight=newLight(); LightOnCommandlightOn=newLightOnCommand(light); remote.setCommand(lightOn); remote.buttonWasPressed(); }}命令模式將請求封裝成對象，使用不同的請求、隊列或日志來參數化其他對象。命令模式支持可撤銷操作。將請求封裝成對象，什么對象？對象將接受者和動作包在內部，只有一個execute接口，外部調用這個接口，不知會進行什么樣的操作。多功能遙控器需要控制多個設備，每一個設備都有開關按鈕需要一個命令組，來控制設備組：起居室燈，廚房燈，吊扇，車庫門，音響，等publicclassRemoteControl{ Command[]onCommands; Command[]offCommands;

publicRemoteControl(){ onCommands=newCommand[7]; offCommands=newCommand[7];

CommandnoCommand=newNoCommand(); for(inti=0;i<7;i++){ onCommands[i]=noCommand; offCommands[i]=noCommand; } }

publicvoidsetCommand(intslot,CommandonCommand,CommandoffCommand){ onCommands[slot]=onCommand; offCommands[slot]=offCommand; }publicvoidonButtonWasPushed(intslot){ onCommands[slot].execute(); } publicvoidoffButtonWasPushed(intslot){ offCommands[slot].execute(); }publicclassLightOffCommandimplementsCommand{

？？

}NoCommand它是一個空對象，稱監視對象，避免了判斷

if(onCommand[slot]!=null)onCommand[slot].execute();撤銷命令有時應該允許后悔，允許命令撤銷。publicinterfaceCommand{ publicvoidexecute(); publicvoidundo();}publicclassLightOffCommandimplementsCommand{ Lightlight;

publicLightOffCommand(Lightlight){ this.light=light; }

publicvoidexecute(){ light.off(); }

publicvoidundo(){ light.on(); }}使用撤銷命令的遙控器代碼測試代碼使用狀態實現撤銷吊扇代碼加入撤銷到吊扇的命令類代碼其它幾個low,medium,off.如何實現。測試吊扇類代碼遙控器的party模式產生一個新的命令，可以讓所有設備打開。publicclassMacroCommandimplementsCommand{ Command[]commands; publicMacroCommand(Command[]commands){ mands=commands; } publicvoidexecute(){ for(inti=0;i<commands.length;i++){ commands[i].execute(); } } publicvoidundo(){ for(inti=0;i<commands.length;i++){ commands