Java如何判断一个url是否有效

import java.io.InputStream;
import java.net.URL;
public class URLTest {
	public static boolean isUrlValid(String strLink) {
        URL url;
        try {
            url = new URL(strLink);
            HttpURLConnection connt = (HttpURLConnection)url.openConnection();
            //也可以通过判断code码判断是否有效 
            //一般是返回200 但是不保证有些网站请求成功返回的不是200
            int responseCode = connt .getResponseCode();
            if(200 == responseCode){
			//链接有效
			}else{
			//链接无效	
			}
            connt.setRequestMethod("HEAD");
            String strMessage = connt.getResponseMessage();
            if (strMessage.compareTo("Not Found") == 0) {
                return false;
            }
            connt.disconnect();
        } catch (Exception e) {
            return false;
        }
        return true;
    }
}

import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;
public class URLValidator {
    public static void main(String[] args) {
        String url = "https://www.google.com";
        boolean isValid = isValidURL(url);
        System.out.println("Is " + url + " valid? " + isValid);
    }
    public static boolean isValidURL(String url) {
        try {
            URLConnection conn = new URL(url).openConnection();
            conn.connect();
            return true;
        } catch (IOException e) {
            return false;
        }
    }
}

package com.url;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
public class TestUrl {
    public static void main(String[] args) {
        testUrl("http://1.3.3.3/test");
        //最好使用下面这个，上面那个超时时间不定，所以可能会导致卡住的情况
        testUrlWithTimeOut("http://1.3.3.3", 2000);
    }
    public static void testUrl(String urlString){
        long lo = System.currentTimeMillis();
        URL url;  
        try {  
             url = new URL(urlString);  
             InputStream in = url.openStream();  
             System.out.println("连接可用");  
        } catch (Exception e1) {  
             System.out.println("连接打不开!");  
             url = null;  
        }  
        System.out.println(System.currentTimeMillis()-lo);
    }
    public static void testUrlWithTimeOut(String urlString,int timeOutMillSeconds){
        long lo = System.currentTimeMillis();
        URL url;  
        try {  
             url = new URL(urlString);  
             URLConnection co =  url.openConnection();
             co.setConnectTimeout(timeOutMillSeconds);
             co.connect();
             System.out.println("连接可用");  
        } catch (Exception e1) {  
             System.out.println("连接打不开!");  
             url = null;  
        }  
        System.out.println(System.currentTimeMillis()-lo);
    }
}