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命令模式
package com.tc.order;
/**命令模式 就是发出命令的对象与执行命令的对象解耦。两者通过中介者传递，命令封装了接收者以及
* 要执行的n个动作中介者不需要知道传递的对象信息。命令可以撤销，如下面的undo()
* 命令接口
*/
public interface Command {
/**
* 执行命令
*/
public void execute();
/**
* 回滚操作
*/
public void undo();
}
package com.tc.order;
//要操作的对象
public class Light {
public void on() {
System.out.println("the light is on.");
}
public void off() {
System.out.println("the light is off.");
}
}
package com.tc.order;
//关灯操作命令
public class LightOffCommand implements Command {
private Light light;
public LightOffCommand(Light light) {
this.light = light;
}
@Override
public void execute() {
light.off();
}
@Override
public void undo() {
light.on();
}
}
package com.tc.order;
//开灯操作命令
public class LightOnCommand implements Command {
private Light light;
public LightOnCommand(Light light) {
this.light = light;
}
@Override
public void execute() {
light.on();
}
@Override
public void undo() {
light.off();
}
}
package com.tc.order;
import java.util.ArrayList;
import java.util.List;
/**
* 遥控器类
*/
public class RemoteControl {
private List<Command> onCommands;
private List<Command> offCommands;
private Command undoCommand;
public RemoteControl() {
onCommands = new ArrayList<Command>();
offCommands = new ArrayList<Command>();
}
public void setCommand(int index, Command onCommand, Command offCommand) {
int size = onCommands.size();
if (size == index) {
onCommands.add(null);
offCommands.add(null);
} else if (size < index) {
throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + size);
}
onCommands.set(index, onCommand);
offCommands.set(index, offCommand);
}
public void onButtonWasPushed(int index) {
Command command = onCommands.get(index);
command.execute();
undoCommand = command;
}
public void offButtonWasPushed(int index) {
Command command = offCommands.get(index);
command.execute();
undoCommand = command;
}
public void undoButtonWasPushed() {
if (null == undoCommand) {
throw new IllegalArgumentException("can not undo.");
}
undoCommand.undo();
}
}
package com.tc.order;
//测试类
public class Test1 {
public static void main(String[] args) {
Light light = new Light();
LightOnCommand lightOnCommand = new LightOnCommand(light);
LightOffCommand lightOffCommand = new LightOffCommand(light);
RemoteControl remoteControl = new RemoteControl();
remoteControl.setCommand(0, lightOnCommand, lightOffCommand);
remoteControl.offButtonWasPushed(0);
remoteControl.undoButtonWasPushed();
}
}
命令模式