将命令封装成对象中,具有以下作用:
设计一个遥控器,可以控制电灯开关。
public interface Command {
void execute();
}
public class LightOnCommand implements Command {
Light light;
public LightOnCommand(Light light) {
this.light = light;
}
@Override
public void execute() {
light.on();
}
}
public class LightOffCommand implements Command {
Light light;
public LightOffCommand(Light light) {
this.light = light;
}
@Override
public void execute() {
light.off();
}
}
public class Light {
public void on() {
System.out.println("Light is on!");
}
public void off() {
System.out.println("Light is off!");
}
}
/**
* 遥控器
*/
public class Invoker {
private Command[] onCommands;
private Command[] offCommands;
private final int slotNum = 7;
public Invoker() {
this.onCommands = new Command[slotNum];
this.offCommands = new Command[slotNum];
}
public void setOnCommand(Command command, int slot) {
onCommands[slot] = command;
}
public void setOffCommand(Command command, int slot) {
offCommands[slot] = command;
}
public void onButtonWasPushed(int slot) {
onCommands[slot].execute();
}
public void offButtonWasPushed(int slot) {
offCommands[slot].execute();
}
}
public class Client {
public static void main(String[] args) {
Invoker invoker = new Invoker();
Light light = new Light();
Command lightOnCommand = new LightOnCommand(light);
Command lightOffCommand = new LightOffCommand(light);
invoker.setOnCommand(lightOnCommand, 0);
invoker.setOffCommand(lightOffCommand, 0);
invoker.onButtonWasPushed(0);
invoker.offButtonWasPushed(0);
}
}