观察者模式股票问题源代码及uml图

以下是观察者模式股票问题的源代码及 UML 图：

import java.util.ArrayList;
import java.util.List;

// Subject（目标）接口
interface Subject {
    void registerObserver(Observer o);
    void removeObserver(Observer o);
    void notifyObservers();
}

// ConcreteSubject（具体目标）类
class StockData implements Subject {
    private List<Observer> observers;
    private double price;
    
    public StockData() {
        observers = new ArrayList<>();
    }
    
    @Override
    public void registerObserver(Observer o) {
        observers.add(o);
    }
    
    @Override
    public void removeObserver(Observer o) {
        observers.remove(o);
    }
    
    @Override
    public void notifyObservers() {
        for (Observer o : observers) {
            o.update(price);
        }
    }
    
    public void setPrice(double price) {
        this.price = price;
        notifyObservers();
    }
}

// Observer（观察者）接口
interface Observer {
    void update(double price);
}

// ConcreteObserver（具体观察者）类
class StockBuyer implements Observer {
    private String name;
    
    public StockBuyer(String name) {
        this.name = name;
    }
    
    @Override
    public void update(double price) {
        System.out.println(name + " received new stock price: " + price);
    }
}

// Client（客户端）类
public class Client {
    public static void main(String[] args) {
        StockData stockData = new StockData();
        
        StockBuyer buyer1 = new StockBuyer("Buyer 1");
        StockBuyer buyer2 = new StockBuyer("Buyer 2");
        StockBuyer buyer3 = new StockBuyer("Buyer 3");
        
        stockData.registerObserver(buyer1);
        stockData.registerObserver(buyer2);
        stockData.registerObserver(buyer3);
        
        stockData.setPrice(50.0);
        
        stockData.removeObserver(buyer2);
        
        stockData.setPrice(55.0);
    }
}

UML 图如下：