设计模式：观察者模式-observer

定义对象间的一种一对多的依赖关系，当一个对象的状态发生变化时，所有依赖于它的对象都得到通知并被自动更新

代码

public class Main {

public static void main(String[] args) {
SubjectImp mySubject=new SubjectImp();
mySubject.setObserver(new Observer01());
mySubject.setObserver(new Observer02());
mySubject.setObserver(new Observer03());

mySubject.update();
}

}

public interface Observer {

public void update();
}

public abstract class Subject {

List<Observer> observer=new ArrayList<Observer>();

public boolean setObserver(Observer o){
try{
observer.add(o);
}catch(Exception e){
System.out.println(e);
return false;
}
return true;
}

public boolean delObserver(Observer o){
try{
observer.remove(o);
}catch(Exception e){
System.out.println(e);
return false;
}
return true;
}

public
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void Notify(){
for(int i=0;i<observer.size();i++){
observer.get(i).update();
}
}

}

public class SubjectImp extends Subject {

public void update(){
System.out.println("========subject is update===========");
Notify();
}
}

public class Observer01 implements Observer {

@Override
public void update() {
System.out.println("observer update 01");
}

}

public class Observer02 implements Observer {

@Override
public void update() {
System.out.println("observer update 02");
}

}

public class Observer03 implements Observer {

@Override
public void update() {
System.out.println("observer update 03");
}

}