设计模式之Java自定义观察者模式

﹏ヽ暗。殇╰゛Y 2022-07-16 09:59 63阅读 0赞

观察者接口：

/**
     * Created by cuboo on 2016/10/14.
     */
    public interface Observer {
        public <T> void update(Observable o,T agr);
    
    }

观察者具体实现类：

/**
     * Created by cuboo on 2016/10/14.
     */
    public class concreteObserver implements Observer {
        private  String[] Message;
        private  String obsName;
        //重写update获得被观察者的数据
        @Override
        public <T> void update(Observable o, T agr) {
            this.Message = (String[]) agr;
            this.obsName = o.getObsName();
        }
        public void print(){
            System.out.println(obsName+":");
            for (String s :
                    Message) {
                System.out.print(s +" ");
            }
            System.out.println();
        }
    }

被观察者抽象类：

import java.util.ArrayList;
    
    /**
     * Created by cuboo on 2016/10/14.
     */
    public abstract class Observable {
        private boolean change = false;
        private String obsName;
        private ArrayList<Observer> Observers = new ArrayList<>();
        //添加观察者
        public synchronized void addObserver(Observer o){
            if (o == null)
                throw new NullPointerException();
            if (!Observers.contains(o)){
                Observers.add(o);
            }
        }
    
        //删除观察者
        public synchronized void deleteObserver(Observer o){
             if (o == null)
                 throw new NullPointerException();
             if (Observers.contains(o)){
                 Observers.remove(o);
             }
        }
    
        //通知观察者
        public <T> void notifyObserver(T agrs){
            synchronized (this){
                if (change){
                    clearChange();
                    for (Observer o:Observers) {
                        o.update(this,agrs);
                    }
                }
            }
        }
        //统计注册的观察者数量
        public synchronized int countObservers(){
            return Observers.size();
        }
    
        //被观察者是否改变
        public synchronized boolean isChanged(){
            return change;
        }
    
        protected synchronized void setChange(){
            change = true;
        }
        private synchronized void clearChange(){
            change = false;
        }
    
        public void setObsName(String obsName) {
            this.obsName = obsName;
        }
    
        public String getObsName() {
            return obsName;
        }
    }

被观察者具体实现类：

/**
     * Created by cuboo on 2016/10/14.
     */
    public class concreteObservable extends Observable {
        private String[] Message;
    
        public void setMessage(String[] message) {
            Message = message;
        }
    
        public String[] getMessage() {
            return Message;
        }
    
        public void notifyObserver() {
            this.setChange();
            this.notifyObserver(getMessage());
        }
    }

示例：

/**
     * Created by cuboo on 2016/10/14.
     */
    public class observertest {
        public static void main(String agrs[]){
            concreteObservable cob = new concreteObservable();
            concreteObserver observer = new concreteObserver();
            concreteObserver observer1 = new concreteObserver();
    
            cob.setObsName("this is ObservableA test");
            cob.setMessage(new String[]{"1","2","3","4"});
            cob.addObserver(observer);
            cob.addObserver(observer1);
    
            cob.notifyObserver();
            System.out.println(cob.countObservers());
            observer.print();
            observer1.print();
    
        }
    }