【GOF23设计模式】_观察者模式_广播机制_消息订阅_网络游戏对战原理_自带类与接口JAVA251-252

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一、S03E251_01【GOF23设计模式】_观察者模式、广播机制、消息订阅、网络游戏对战原理

package com.test.observer;import java.util.ArrayList;import java.util.List;public class Subject {    protected List<Observer> list = new ArrayList<Observer>();    public void registerObserver(Observer obs){        list.add(obs);    }    public void removeObserver(Observer obs){        list.remove(obs);    }    //通知所有的观察者更新状态    public void notjfyAllObservers(){        for (Observer obs : list) {            obs.update(this);        }    }}

package com.test.observer;public class ConcreteSubject extends Subject{    private int state;    public int getState() {        return state;    }    public void setState(int state) {        this.state = state;        //主题对象(目标对象)的值发生了变化，请通知所有的观察者        this.notjfyAllObservers();    }}

package com.test.observer;public interface Observer {    void update(Subject subject);}

package com.test.observer;public class ObserverA implements Observer{    private int myState;//myState需要跟目标对象的state值保持一致    public int getMyState() {        return myState;    }    public void setMyState(int myState) {        this.myState = myState;    }    @Override    public void update(Subject subject) {        myState = ((ConcreteSubject)subject).getState();     }}

package com.test.observer;public class Client {    public static void main(String[] args) {        //目标对象        ConcreteSubject subject = new ConcreteSubject();        //创建多个观察者        ObserverA obs1 = new ObserverA();        ObserverA obs2 = new ObserverA();        ObserverA obs3 = new ObserverA();        //将这三个观察者添加到subject对象的观察者队伍中        subject.registerObserver(obs1);        subject.registerObserver(obs2);        subject.registerObserver(obs3);        //改变subject的状态        subject.setState(3000);        System.out.println("#################");        //我们看看，观察者的状态是不是也发生了变化        System.out.println(obs1.getMyState());        System.out.println(obs2.getMyState());        System.out.println(obs3.getMyState());        //改变subject的状态        subject.setState(30);        System.out.println("#################");        //我们看看，观察者的状态是不是也发生了变化        System.out.println(obs1.getMyState());        System.out.println(obs2.getMyState());        System.out.println(obs3.getMyState());    }}

控制台输出：#################300030003000#################303030

二、S03E252_01【GOF23设计模式】_观察者模式、obserable类和observer接口、应用场景总结

package com.test.observer2;import java.util.Observable;/** * 目标对象 */public class ConcreteSubject extends Observable{    private int state;    public int getState() {        return state;    }    public void setState(int state) {        this.state = state;    }    public void set(int s){        state = s;  //目标对象的状态发生了改变        setChanged();   //表示目标对象已经做了更改        notifyObservers(state); //通知所有的观察者    }}

package com.test.observer2;import java.util.Observable;import java.util.Observer;public class ObserverA implements Observer{    private int myState;    public int getMyState() {        return myState;    }    public void setMyState(int myState) {        this.myState = myState;    }    @Override    public void update(Observable o, Object arg) {        myState = ((ConcreteSubject)o).getState();    }}

package com.test.observer2;public class Client {    public static void main(String[] args) {        //创建目标对象Obserable        ConcreteSubject subject = new ConcreteSubject();        //创建观察者        ObserverA obs1 = new ObserverA();        ObserverA obs2 = new ObserverA();        ObserverA obs3 = new ObserverA();        //将上面三个观察者对象添加到目标对象subject的观察者容器中        subject.addObserver(obs1);        subject.addObserver(obs2);        subject.addObserver(obs3);        //改变subject对象的状态        subject.set(3000);        System.out.println("==================状态修改了");        //观察者的状态发生了变化        System.out.println(obs1.getMyState());        System.out.println(obs2.getMyState());        System.out.println(obs3.getMyState());        //改变subject对象的状态        subject.set(600);        System.out.println("==================状态修改了");        //观察者的状态发生了变化        System.out.println(obs1.getMyState());        System.out.println(obs2.getMyState());        System.out.println(obs3.getMyState());    }}

控制台输出：==================状态修改了300030003000==================状态修改了600600600