命令模式的四種角色：

1、接受者（Receiver）負責執行請求的相關操作的一個類

2、命令接口：（Command）用於封裝請求的方法

3、具體命令：（ConcreteCommand）命令接口的具體實現類

4、請求者：（Invoker）包含了命令接口的實例變量，負責調用具體命令

請求者：
package DesignPatterns.CommandMode;

public class Invoker {
    private Command command;

    public void setCommand(Command command) {
        
 
this.command = command;
    }
    public void startCommand(){
        command.execute();
    }
}

命令接口：
package DesignPatterns.CommandMode;

public interface Command {
    public void execute();
}

具體命令：

package DesignPatterns.CommandMode;

public class ConcreteCommand implements Command{
    private Receiver receiver;
 
    public ConcreteCommand(Receiver receiver)
    {
        this.receiver=receiver;
    }
    public void execute()
    {
        receiver.printCommand();
    }


}

接受者：

package DesignPatterns.CommandMode;

public class Receiver {
    public void printCommand()
    {
        System.out.println("執行命令");
    }

}

測試類：
 

package DesignPatterns.CommandMode;

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

    }
}

命令模式（1）