直接上代码，然而没什么用：

try {
            URL pageUrl = new URL("http://www.baidu.com/");
            HttpURLConnection httpUrlConn = (HttpURLConnection) pageUrl
                    .openConnection();
            int statusCode = httpUrlConn.getResponseCode();
            System.out.println(statusCode);
        } catch (Exception e) {
            e.printStackTrace();
        }

网上找了点资料看了看，上面说，这个不能再main这个主线程中跑，要另起一个线程来运行。

于是我就试了下：

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

public class TestUrl {  
    public static void main(String[] args) {  
        Test t = new Test();  
        Thread demo = new Thread(t);  
        demo.start();  
    }  
}  

class Test implements Runnable {  
    @Override  
    public void run() {  
        // TODO Auto-generated method stub  
        try {  
            URL pageUrl = new URL("http://www.baidu.com/");  
            HttpURLConnection httpUrlConn = (HttpURLConnection) pageUrl  
                    .openConnection();  
            int statusCode = httpUrlConn.getResponseCode();  
            System.out.println(statusCode);  
        } catch (Exception e) {  
            e.printStackTrace();  
        }  
    }  
}  

果然没问题了，这里记录下！