测试URL是否可用

import java.net.URL;  
import java.net.HttpURLConnection;  
 
public class test2 {  
    private boolean isConnect(String url) {  
        boolean flag = false;  
        int counts = 0;  
        if (url == null || url.length() <= 0) {  
            return flag;  
        }  

        //测试5次
        while (counts < 5) {  
            try {  
                HttpURLConnection connection = (HttpURLConnection) new URL(url).openConnection();  
                int state = connection.getResponseCode();  
                if (state == 200) {  //200:可用，401不可用
                    flag = true;  
                }  
                break;  
            } catch (Exception ex) {  
                counts++;  
                continue;  
            }  
        }  
        return flag;  
    }  
 
    public static void main(String[] args) {  
        test2 check = new test2();  
        System.out.println(check.isConnect("http://www.baidu.com/"));  
    }  
}