java - 简单的天气预报 Java 代码

Question

我的家庭作业是弄清楚:

• 这段代码的作用
• 存在哪些潜在问题

代码

/// Enum
public enum Event {
    TORNADO, THUNDERSTORM, TSUNAMI, RAIN, SNOW, WIND, COLD, HEAT; 
    public final static String CRITICAL = "Critical";
    public final static String SEVERE = "Severe";
    public final static String MEDIUM = "Medium";
    public final static String LIGHT = "Light";

    private String severity;
    private String location;

    public void setSeverity(String severity) {
        this.severity = severity; 
    }

    public void setLocation(String location) {
        this.location = location; 
    }

    public String toString() {
        return super.toString() + ":" + severity + " at " + location; 
    }
}

///Interface
public interface IEventListener {
    void eventReceived(Event event); 
}

///Class
public class EventPublisher implements IEventListener {
    Map<Event, Collection<IEventListener>> listeners = new HashMap<Event, Collection<IEventListener>>(); 

    @Override 
    public synchronized void eventReceived(Event event) {
        for (IEventListener listener : listeners.get(event)){ 
            listener.eventReceived(event); 
        }
    }

    public synchronized void register(IEventListener listener, Event event){
        Collection<IEventListener> list = listeners.get(event); 
        if (list == null) {
            list = new LinkedList<IEventListener>();
            listeners.put(event, list); 
        }
        list.add(listener);
    }

    public synchronized void deregister(IEventListener listener, Event event) {
        listeners.get(event).remove(listener); 
    }

    public String toString() {
        String ret = ""; 
        Iterator<Event> i = listeners.keySet().iterator();
        while (i.hasNext()) {
            Iterator<IEventListener> j = listeners.get(i.next()).iterator();
            while (j.hasNext()) {
                ret = ret + i.next() + "::" + j.next() + "\n"; 
            }
        }
        return ret; 
    }
}

我浏览了代码，发现该代码尝试生成天气报告并根据 eventReceived 对天气状况进行分类(Event 可以注册/取消注册) .

但是我看不出代码有任何问题。我的老师坚持认为存在问题。谁能帮我吗？

Answer 1

首先，Event 不应该是enum。因为它的成员实际上都是单例；通过改变例如一个TORNADO的严重性，您可以更改全部的严重性。您应该有一个 EventType 枚举、一个 Severity 枚举以及一个使用它们的 Event 类。

然后，您在事件发布者内的 map 将会改变...

此外，deregister 方法可能会引发空引用异常...