为什么系统好像可以自动跳出这个while循环

以下是局部完整代码：

new Thread(new Runnable() {

@Override

public void run() {

HttpURLConnection connection_koudai = null;

try{

//open a HTTP request

URL url = new URL("http://www.koudaidaxue.com/login/applogin.php");

connection_koudai = (HttpURLConnection) url.openConnection();

connection_koudai.setRequestMethod("POST");

//send cookie to server

connection_koudai.setRequestProperty("Cookie", COOKIE);

DataOutputStream out = new DataOutputStream(connection_koudai.getOutputStream());

out.writeBytes("userid=60040&&password=18780682697");

connection_koudai.setConnectTimeout(1000);

connection_koudai.setReadTimeout(1000);

//get cookie from response

COOKIE = connection_koudai.getHeaderField("Set-Cookie");

Log.d("get_cookie","cookiej is:"+COOKIE);

Log.d("test","open");

//deal with data that has been sent back

InputStream in_koudai = connection_koudai.getInputStream();

BufferedReader reader = new BufferedReader(new InputStreamReader(in_koudai));

StringBuilder response = new StringBuilder();

String line;
while ((line = reader.readLine()) != null){

response.append(line);

}

Log.d("test","get");

//store data into message

Message message = new Message();

message.what = SHOW_RESPONSE;

message.obj = response.toString();

handler.sendMessage(message);

}catch (Exception e) {

e.printStackTrace();

}finally{

if(connection_koudai!=null){

connection_koudai.disconnect();

Log.d("test","close");

}

}

}

//.start() open the thread

}).start();