java RUL是否有效

package com.ddln.test;

import java.net.HttpURLConnection;
import java.net.URL;

/** 
* 文件名称为：URLAvailability.java 
* 文件功能简述： 描述一个URL地址是否有效 
* @author Jason 
* @time 2010-9-14 
* 
*/ 
public class URLAvailability { 
private static URL url; 
private static HttpURLConnection con; 
private static int state = -1; 

/** 
* 功能：检测当前URL是否可连接或是否有效, 
* 描述：最多连接网络 5 次, 如果 5 次都不成功，视为该地址不可用 
* @param urlStr 指定URL网络地址 
* @return URL 
*/ 
public synchronized static URL isConnect(String urlStr) { 
int counts = 0; 
if (urlStr == null || urlStr.length() <= 0) { 
return null; 
} 

while (counts < 5) { 
try { 
url = new URL(urlStr); 
con = (HttpURLConnection) url.openConnection(); 
state = con.getResponseCode(); 
System.out.println(counts +"= "+state); 
if (state == 200) { 
System.out.println("URL可用！"); 
} 
break; 
}catch (Exception ex) { 
counts++; 
System.out.println("URL不可用，连接第 "+counts+" 次"); 
//     urlStr = null; 
continue; 
} 
}
System.out.println("url"+url);
return url; 
}

}