Simple readline algorithm for Networking

Are there any simple standardized way of reading a full line from a socket that mallocs the memory for you? If so, what are they? If not, is there a way to do it in approximately O(1) time (obviously not including the time for the memory allocation).

BufferedReader r = new BufferedReader(new InputStreamReader(new Socket(host, port).getInputStream()))
String s;
while((s = r.readLine() != null) process(s);
r.close();