question: public static boolean doCheckPoint ( ) { if ( forceChkpt ) { forceChkpt = false ; return true ; } if ( chkptDuration == 0 ) { return false ; } long now = System . currentTimeMillis ( ) ; if ( now - lastChkpt >= TLCGlobals . chkptDuration ) { lastChkpt = now ; return true ; } return false ; }
target:  IMPORTANT NOTE: The method is unsynchronized. It is the caller's responsibility to ensure that only a single thread calls this method.