Java 如何获取远程文件大小

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

public class Main {
   public static void main(String[] argv) 
   throws Exception {
      int size;
      URL url = new URL("http://www.2345.com/i/search0320/baidu_web.gif");
      URLConnection conn = url.openConnection();
      size = conn.getContentLength();
      if (size < 0)
      System.out.println("无法获取文件大小。");
      else
      System.out.println("文件大小为：" +
      + size + " bytes");
      conn.getInputStream().close();
   }
}