我的代码为什么会OutOfMemory

Question

为什么这样写会出现OutOfMemory错误，而第二段那样写就不会？

URL url = new URL(urlStr);
HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();
BufferedReader buffer = new BufferedReader(new InputStreamReader(urlConn.getInputStream()));
line = buffer.readLine();
while(line != null){
sb.append(line);
}

URL url = new URL(urlStr);
HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();
BufferedReader buffer = new BufferedReader(new InputStreamReader(urlConn.getInputStream()));
while ((line = buffer.readLine()) != null) {
sb.append(line);
}

Answer 1

第一段：

line = buffer.readLine();
while (line != null){
    sb.append(line);
}

line 的值始终不变，这是一个死循环，所以 sb 会越来越大。

第二段：

while ((line = buffer.readLine()) != null) {
    sb.append(line);
}

line 的值会不断改变，最后读到流的末尾，readLine() 会返回 null ，于是循环结束。