设计模式（中介者模式）

public abstract class Mediator {
    public abstract void notice(String content);
}

public class ConcreteMediator extends Mediator {
    
    //这里可以有多个目标
    //private Target target1
    //private Target target2
    private Target target;
    
    //也可以构造addTarget以维护一个处理对象的列表
    public ConcreteMediator(){
        target = new ConcreteTarget();
    }
    
    @Override
    public void notice(String content) {
        target.doSomething(content);
    }
}

public abstract class Target {
    public abstract void doSomething(String content);
}

public class ConcreteTarget extends Target {

    @Override
    public void doSomething(String content) {
        System.out.println("ConcreteTarget doSomething" + content);
    }
}

public class App {

    public static void main(String[] args) {
        Mediator mediator = new ConcreteMediator();
        mediator.notice("Fredric");
        
    }
}