先看一下類圖：
具體實現：
package obs.self;
/**
* 被觀察對象
* @author wangfeihu
*
*/
public interface Subject {
/**
* 增加一個觀察者
* @param observer
*/
public void addObserver(Observer observer);
public void removeObserver(Observer observer);
/**
* 通知所有觀察者
* @param msg
*/
public void notifyObservers(Object msg);
}package obs.self;
/**
* 觀察者
* @author wangfeihu
*
*/
public interface Observer {
public void update(Object msg);
}package obs.self;
import java.util.HashSet;
import java.util.Set;
/**
* 銀行賬戶, 餘額發生變化的時候進行相關的通知
* @author wangfeihu
*
*/
public class Account implements Subject {
private int balance = 0;
public Set<Observer> obervers = new HashSet<Observer>();
public void addObserver(Observer observer) {
obervers.add(observer);
}
public void removeObserver(Observer observer) {
obervers.remove(observer);
}
public void notifyObservers(Object msg) {
for (Observer obs : obervers) {
obs.update(msg);
}
}
public int getBalance() {
return balance;
}
public void setBalance(int balance) {
this.balance = balance;
this.notifyObservers("賬戶餘額發生改變," + balance);
}
/**
* 取款
* @param money
*/
public void withdraw(int money) {
this.setBalance(this.balance - money);
}
/**
* 存款
* @param money
*/
public void deposit(int money) {
this.setBalance(this.balance + money);
}
}package obs.self;
public class MobileObserver implements Observer {
public void update(Object msg) {
System.out.println("手機短信提醒：" + msg);
}
}package obs.self;
public class WechatObserver implements Observer {
public void update(Object msg) {
System.out.println("微信服務號提醒：" + msg);
}
}執行：
package obs.self;
public class ObserverTest {
public static void main(String[] args) {
Account accountSubject = new Account();
MobileObserver mobileObserver = new MobileObserver();
WechatObserver wechatObserver = new WechatObserver();
accountSubject.addObserver(mobileObserver);
accountSubject.addObserver(wechatObserver);
// 存錢
accountSubject.deposit(10000);
// 取錢
accountSubject.withdraw(500);
//移除短信通知
accountSubject.removeObserver(mobileObserver);
accountSubject.withdraw(600);
}
}