java - 为什么不能声明抛出异常类？

Question

package com.csl.bps.util;

import java.awt.Event;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.HashMap;

import javax.servlet.ServletContextEvent;

public class Reloader implements Runnable{
    private boolean firstLoad = true;
    private ServletContextEvent eventCopy = null;
    private File configFile = null;
    private String configFilePath = null;
    private HashMap map = null;
    private BufferedReader reader = null;
    private long lastModifiedTime = 0;
    public Reloader(ServletContextEvent event) {
        eventCopy = event;
        //event.getServletContext().setAttribute("i", new Integer(2));
    }

    public void run() {
        configFilePath = (String)eventCopy.getServletContext().getInitParameter("billRunDetailConfig");
        if(configFilePath == null)
        {
            eventCopy.getServletContext().log("Warning: No bill run detail config file found. Please check the file and restart.");
        }
        configFile = new File(configFilePath);
        if(firstLoad == true)
        {
            map = createMap(configFile);
            lastModifiedTime = configFile.lastModified();
            eventCopy.getServletContext().setAttribute("BunRunDetail", map);
            eventCopy.getServletContext().log("\n\nFirst load of bill run detail config file. HashMap loaded.\n");
            firstLoad = false;
        }
        else
        {
            eventCopy.getServletContext().log("\n\nAnother load of bill run detail config file. Checking for the file's last modified time...\n");
            if(configFile.lastModified() != lastModifiedTime)
            {
                map = createMap(configFile);
                lastModifiedTime = configFile.lastModified();
                eventCopy.getServletContext().setAttribute("BunRunDetail", map);
                eventCopy.getServletContext().log("Config file changed. HashMap is hashed again.");
            }else
            {   
                eventCopy.getServletContext().log("Config file is not changed.");
            }
        }
    }

    private HashMap createMap(File configFile){
        HashMap map = null;
        try{
            reader = new BufferedReader(new FileReader(configFile));
        }catch(FileNotFoundException ex){
            ex.printStackTrace();
        }
        return map;
    }
}

我想向任何方法的调用者抛出任何异常，但我不能，例如:我可以这样做:

private HashMap createMap(File configFile) throws FileNotFoundException{
    HashMap map = null;
    try{
        reader = new BufferedReader(new FileReader(configFile));
    }catch(FileNotFoundException ex){
        //ex.printStackTrace();
        throw ex;
    }
    return map;
}

但在上面:

if(firstLoad == true)
{
    map = createMap(configFile);
    lastModifiedTime = configFile.lastModified();
    eventCopy.getServletContext().setAttribute("BunRunDetail", map);
    eventCopy.getServletContext().log("\n\nFirst load of bill run detail config file. HashMap loaded.\n");
    firstLoad = false;
}

在map = createMap(configFile)行中，我在eclipse中提示未处理异常错误，但我只能向其添加一个try catch子句。

我希望它向调用者抛出异常，并让调用者处理异常，因为如果我返回这里，我不确定是否所有资源都已关闭。

<小时/>

为什么它的签名不包含 throws 子句？它是否假设它不会产生任何异常？

如果出现异常，并且我用 try/catch 子句包装它，线程会停止并通知父级吗？

Answer 1

不能在 run() 方法中添加“throws”子句的原因是 run() 是在 Runnable 接口(interface)中定义的，并且其签名不包含 throws 子句。