public class MyLogger { private StringBuilder logger = new StringBuuilder(); public void log(String message, String user) { logger.append(message); logger.append(user); } } The programmer must guarantee that a single MyLogger object works properly for a multi-threaded system. How must this code be changed to be thread-safe?()
A. synchronize the log method
B. replace StringBuilder with StringBuffer
C. No change is necessary, the current MyLogger code is already thread-safe.
D. replace StringBuilder with just a String object and use the string concatenation (+=) within the log method