command

参考 http://en.wikipedia.org/wiki/Command_pattern

/*the Invoker class*/ public class Switch { private Command flipUpCommand; private Command flipDownCommand; public Switch(Command flipUpCmd, Command flipDownCmd) { this.flipUpCommand = flipUpCmd; this.flipDownCommand = flipDownCmd; } public void flipUp() { flipUpCommand.execute(); } public void flipDown() { flipDownCommand.execute(); } } /*Receiver class*/ public class Light { public Light() { } public void turnOn() { System.out.println("The light is on"); } public void turnOff() { System.out.println("The light is off"); } } /*the Command interface*/ public interface Command { void execute(); } /*the Command for turning on the light*/ public class FlipUpCommand implements Command { private Light theLight; public FlipUpCommand(Light light) { this.theLight=light; } public void execute(){ theLight.turnOn(); } } /*the Command for turning off the light*/ public class FlipDownCommand implements Command { private Light theLight; public FlipDownCommand(Light light) { this.theLight=light; } public void execute() { theLight.turnOff(); } } /*The test class or client*/ public class PressSwitch { public static void main(String[] args) { Light lamp = new Light(); Command switchUp = new FlipUpCommand(lamp); Command switchDown = new FlipDownCommand(lamp); // See criticism of this model above: // The switch itself should not be aware of lamp details (switchUp, switchDown) // either directly or indirectly Switch s = new Switch(switchUp,switchDown); try { if (args[0].equalsIgnoreCase("ON")) { s.flipUp(); } else if (args[0].equalsIgnoreCase("OFF")) { s.flipDown(); } else { System.out.println("Argument /"ON/" or /"OFF/" is required."); } } catch (Exception e){ System.out.println("Arguments required."); } } } =====================

java tip (http://www.javaworld.com/javaworld/javatips/jw-javatip68.html?page=3) 给了类似的例子，多了Fan作为receiver:

TestCommand.java class Fan {         public void startRotate() {                 System.out.println("Fan is rotating");         }         public void stopRotate() {                 System.out.println("Fan is not rotating");         } } class Light {         public void turnOn( ) {                 System.out.println("Light is on ");         }         public void turnOff( ) {                 System.out.println("Light is off");         } } class Switch {         private Command UpCommand, DownCommand;         public Switch( Command Up, Command Down) {                 UpCommand = Up; // concrete Command registers itself with the invoker                 DownCommand = Down;         }         void flipUp( ) { // invoker calls back concrete Command, which executes the Command on the receiver                         UpCommand . execute ( ) ;                                   }         void flipDown( ) {                         DownCommand . execute ( );         } } class LightOnCommand implements Command {         private Light myLight;         public LightOnCommand ( Light L) {                 myLight  =  L;         }         public void execute( ) {                 myLight . turnOn( );         } } class LightOffCommand implements Command {         private Light myLight;         public LightOffCommand ( Light L) {                 myLight  =  L;         }         public void execute( ) {                 myLight . turnOff( );         } } class FanOnCommand implements Command {         private Fan myFan;         public FanOnCommand ( Fan F) {                 myFan  =  F;         }         public void execute( ) {                 myFan . startRotate( );         } } class FanOffCommand implements Command {         private Fan myFan;         public FanOffCommand ( Fan F) {                 myFan  =  F;         }         public void execute( ) {                 myFan . stopRotate( );         } } public class TestCommand {                 public static void main(String[] args) {                         Light  testLight = new Light( );                         LightOnCommand testLOC = new LightOnCommand(testLight);                         LightOffCommand testLFC = new LightOffCommand(testLight);                         Switch testSwitch = new Switch( testLOC,testLFC);                               testSwitch.flipUp( );                         testSwitch.flipDown( );                         Fan testFan = new Fan( );                         FanOnCommand foc = new FanOnCommand(testFan);                         FanOffCommand ffc = new FanOffCommand(testFan);                         Switch ts = new Switch( foc,ffc);                         ts.flipUp( );                         ts.flipDown( );                 } }               Command.java public interface Command {         public abstract void execute ( ); }