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

public class Main {
    public static void main(String[] argv) throws Exception {
        URL u = new URL("http://127.0.0.1/java.bmp");
        URLConnection uc = u.openConnection();
        uc.setUseCaches(false);
        long timestamp = uc.getLastModified();
        System.out.println("java.bmp 文件最后修改时间 :"+timestamp);
    }
}

java.bmp 文件最后修改时间 24 May 2014 12:14:50