《Head First设计模式》阅读笔记.第六章

臧圩人

// 遥控器
public class RemoteControl {
        private Command[] leftCommands;

        private Command[] rightCommands;

        private Command prevCommand;

        public RemoteControl() {
                leftCommands = new Command[3];
                rightCommands = new Command[3];

                for (int i = 0; i < leftCommands.length; i++) {
                        leftCommands = new NoCommand();
                }
                for (int i = 0; i < rightCommands.length; i++) {
                        rightCommands = new NoCommand();
                }

                prevCommand = new NoCommand();
        }

        public void setCommand(int index, Command left, Command right) {
                leftCommands[index] = left;
                rightCommands[index] = right;
        }

        public void leftButtonPressed(int index) {
                System.out.println("Left button [" + index + "] is pressed.");
                leftCommands[index].execute();
                prevCommand = leftCommands[index];
        }

        public void rightButtonPressed(int index) {
                System.out.println("Right button [" + index + "] is pressed.");
                rightCommands[index].execute();
                prevCommand = rightCommands[index];
        }

        public void cancelButtonPressed() {
                System.out.println("Cancel button is pressed.");
                prevCommand.undo();
        }
}

臧圩人

// 空命令，处理空对象（null object）
public class NoCommand implements Command {
        public void execute() {
        }

        public void undo() {
        }
}

臧圩人

----命令（Command）模式测试程序----
// 测试程序
public class TestRemoteControl {
        public static void main(String[] args) {
                RemoteControl rc = new RemoteControl();

                Mp3Player player = new Mp3Player("Sony Ericsson");
                PlayMusicCommand pm = new PlayMusicCommand(player);
                StopMusicCommand sm = new StopMusicCommand(player);
                rc.setCommand(0, pm, sm);

                Radio radio = new Radio("Tecsun");
                RadioOnCommand ron = new RadioOnCommand(radio);
                RadioOffCommand roff = new RadioOffCommand(radio);
                FrequencyHigherCommand fh = new FrequencyHigherCommand(radio);
                FrequencylowerCommand fl = new FrequencylowerCommand(radio);
                rc.setCommand(1, ron, roff);
                rc.setCommand(2, fh, fl);
               
                rc.leftButtonPressed(0);
                rc.cancelButtonPressed();
                rc.leftButtonPressed(0);
                rc.rightButtonPressed(0);
                rc.cancelButtonPressed();
               
                rc.leftButtonPressed(1);
                rc.cancelButtonPressed();
                rc.leftButtonPressed(1);
                rc.rightButtonPressed(1);
                rc.cancelButtonPressed();
               
                rc.leftButtonPressed(2);
                rc.cancelButtonPressed();
                rc.leftButtonPressed(2);
                rc.rightButtonPressed(2);
                rc.cancelButtonPressed();
        }
}

----测试程序运行结果----
Left button [0] is pressed.
Music is playing.
Cancel button is pressed.
Music is stopped.
Left button [0] is pressed.
Music is playing.
Right button [0] is pressed.
Music is stopped.
Cancel button is pressed.
Music is playing.
Left button [1] is pressed.
Radio is on.
Cancel button is pressed.
Radio is off.
Left button [1] is pressed.
Radio is on.
Right button [1] is pressed.
Radio is off.
Cancel button is pressed.
Radio is on.
Left button [2] is pressed.
Frequency is set to 100.1
Cancel button is pressed.
Frequency is set to 100.0
Left button [2] is pressed.
Frequency is set to 100.1
Right button [2] is pressed.
Frequency is set to 100.0
Cancel button is pressed.
Frequency is set to 100.1

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臧圩人

3.宏命令（Macro Command）实例

在以上代码基础上完成：
// 宏命令
public class MacroCommand implements Command {
        private Command[] commands;

        public MacroCommand(Command[] commands) {
                this.commands = commands;
        }

        public void execute() {
                for (int i = 0; i < commands.length; i++) {
                        commands.execute();
                }
        }

        public void undo() {
                for (int i = commands.length - 1; i >= 0; i--) {
                        commands.undo();
                }
        }
}

臧圩人

----宏命令（Macro Command）测试程序----
// 测试宏命令
public class TestMacroCommand {
        public static void main(String[] args) {
                Mp3Player player = new Mp3Player("Sony Ericsson");
                PlayMusicCommand pm = new PlayMusicCommand(player);
                StopMusicCommand sm = new StopMusicCommand(player);

                Radio radio = new Radio("Tecsun");
                RadioOnCommand ron = new RadioOnCommand(radio);
                RadioOffCommand roff = new RadioOffCommand(radio);
                FrequencyHigherCommand fh = new FrequencyHigherCommand(radio);
                FrequencylowerCommand fl = new FrequencylowerCommand(radio);
                FrequencyHigherCommand fh2 = new FrequencyHigherCommand(radio);
                FrequencylowerCommand fl2 = new FrequencylowerCommand(radio);

                Command[] commands = new Command[] { pm, sm, ron, fh, fh2, fl, fl2, roff };
                MacroCommand mc = new MacroCommand(commands);

                RemoteControl rc = new RemoteControl();
                rc.setCommand(0, mc, mc);
                rc.leftButtonPressed(0);
                rc.cancelButtonPressed();
        }
}

----测试程序运行结果----
Left button [0] is pressed.
Music is playing.
Music is stopped.
Radio is on.
Frequency is set to 100.1
Frequency is set to 100.2
Frequency is set to 100.1
Frequency is set to 100.0
Radio is off.
Cancel button is pressed.
Radio is on.
Frequency is set to 100.1
Frequency is set to 100.2
Frequency is set to 100.1
Frequency is set to 100.0
Radio is off.
Music is playing.
Music is stopped.

--------

臧圩人

4.聪明命令（Smart Command）实例

在以上代码基础上完成：
// 聪明（Smart）命令实例
public class PrintLogCommand implements Command {
        public void execute() {
                // 自己实现，而不是委托其它类
                System.out.println("Log at " + new Date());
        }

        public void undo() {
                // 命令可以支持撤销，也可以不支持
        }
}

臧圩人

----聪明命令（Smart Command）测试程序----
// 测试聪明命令
public class TestSmartCommand {
        public static void main(String[] args) {
                PrintLogCommand pl = new PrintLogCommand();
                RemoteControl rc = new RemoteControl();
                rc.setCommand(0, pl, pl);
                rc.leftButtonPressed(0);
        }
}

----测试程序运行结果----
Left button [0] is pressed.
Log at Tue Jan 19 14:44:02 CST 2010

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臧圩人

本该昨天完成的，晚了一天，要加紧

justforregister

nice job