命令模式：将一个请求封装为一个对象，从而可以用不同的请求对客户进行参数化；对请求排队或记录请求日志，以及支持可撤销的操作。

 

public abstract class Command {    protected Receiver receiver;    public Command(Receiver receiver) {        this.receiver = receiver;    }    public abstract void execute();}

 

public class ConcreteCommand extends Command {    public ConcreteCommand(Receiver receiver) {        super(receiver);    }    @Override    public void execute() {        receiver.action();    }}

 

public class Receiver {    public void action() {        System.out.println("执行请求！");    }}

 

public class Invoker {    private Command command;    public void setCommand(Command command) {        this.command = command;    }    public void executeCommand() {        command.execute();    }}

 

public class CommandDemo {    public static void main(String[] args) {        Receiver receiver = new Receiver();        Command command = new ConcreteCommand(receiver);        Invoker invoker = new Invoker();        invoker.setCommand(command);        invoker.executeCommand();    }}