需求：主体有两种事件，观察者可以任意关注其中的某个事件或全部事件，当主体事件发生，通知对应的观察者。
例如：主体是商场，有新货上架和降价两种事件，消费者可以关注其中的一种或全部事件，当降价了，可以通知所有关注降价的消费者。
目录：
主体：
import java.util.ArrayList;
import java.util.List;
public abstract class Observable {
private List
private List
public void attachone(Observer observer) {
listone.add(observer);
System.out.println("添加一个上架观察者");
}
public void detachone(Observer observer) {
listone.remove(observer);
}
public void nodifyObserversone(String newState) {
for(Observer observer:listone) {
observer.updateone(newState);
}
}
public void attachtwo(Observer observer) {
listtwo.add(observer);
System.out.println("添加一个降价观察者");
}
public void detachtwo(Observer observer) {
listtwo.remove(observer);
}
public void nodifyObserverstwo(String newState) {
for(Observer observer:listtwo) {
observer.updatetwo(newState);
}
}
}
具体主体：
public class Market extends Observable{
private String putawaystate;
private String depreciatestate;
public String getPutawayState() {
return putawaystate;
}
public String getDepreciateState() {
return depreciatestate;
}
public void changeputawaystate(String newState) {
putawaystate =newState;
System.out.println("发布主题状态："+putawaystate);
this.nodifyObserversone(putawaystate);
}
public void changedepreciatestate(String newState) {
depreciatestate =newState;
System.out.println("发布主题状态："+depreciatestate);
this.nodifyObserverstwo(depreciatestate);
}
}
观察者：
public abstract class Observer {
private String name;
public Observer(String name) {
this.name=name;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name=name;
}
public abstract void updateone(String state);
public abstract void updatetwo(String state);
}
具体观察者：
public class Consumer extends Observer{
public Consumer(String name) {
super(name);
}
private String putawaystate;
private String depreciatestate;
public void updateone(String state) {
putawaystate =state;
System.out.println(super.getName()+"状态为："+putawaystate);
}
public void updatetwo(String state) {
depreciatestate =state;
System.out.println(super.getName()+"状态为："+depreciatestate);
}
}
客户端：
public class Client {
public static void main(String[] args) {
Market market = new Market();
Observer observerthree =new Consumer("1");
market.attachone(observerthree);
market.attachtwo(observerthree);
market.changeputawaystate("商品B上架");
market.changedepreciatestate("商品B降价");
System.out.println("~~~~~~~~~~~");
Observer observerone =new Consumer("2");
market.attachone(observerone);
market.changeputawaystate("商品A上架");
System.out.println("~~~~~~~~~~~");
Observer observertwo =new Consumer("3");
market.attachtwo(observertwo);
market.changedepreciatestate("商品A降价");
System.out.println("~~~~~~~~~~~");
}
}
实验结果：
类图：
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