publicclassMyLogger{privateStringBuilderlogger=newStringBuuilder（）；publicvoidlog（Stringmessage，Stringuser）{logger.append（message）；logger.append（user）；}}TheprogrammermustguaranteethatasingleMyLoggerobjectworksproperlyforamulti-threadedsystem.Howmustthiscod
题目
publicclassMyLogger{privateStringBuilderlogger=newStringBuuilder（）；publicvoidlog（Stringmessage，Stringuser）{logger.append（message）；logger.append（user）；}}TheprogrammermustguaranteethatasingleMyLoggerobjectworksproperlyforamulti-threadedsystem.Howmustthiscodebechangedtobethread-safe？（）
A.synchronizethelogmethod
B.replaceStringBuilderwithStringBuffer
C.Nochangeisnecessary，thecurrentMyLoggercodeisalreadythread-safe.
D.replaceStringBuilderwithjustaStringobjectandusethestringconcatenation（+=）withinthelogmethod