void rolloverWithLock(final boolean force) throws IOException {
  writeLock.lock();
  try {
    rollover(force);
  }
  finally {
    writeLock.unlock();
  }
}

void rolloverWithLock ( final boolean force ) throws IOException { writeLock . lock ( ) ; try { rollover ( force ) ; } finally { writeLock . unlock ( ) ; } }
method is exposed for unit testing
