code: public void activateOptions() {
          if (rollingPolicy == null) {
              LogLog.warn(
                      "Please set a rolling policy for the RollingFileAppender named '"
                              + getName() + "'");
  
              return;
          }
  
          //
          //  if no explicit triggering policy and rolling policy is both.
          //
          if (
                  (triggeringPolicy == null) && rollingPolicy instanceof TriggeringPolicy) {
              triggeringPolicy = (TriggeringPolicy) rollingPolicy;
          }
  
          if (triggeringPolicy == null) {
              LogLog.warn(
                      "Please set a TriggeringPolicy for the RollingFileAppender named '"
                              + getName() + "'");
  
              return;
          }
  
          Exception exception = null;
  
          synchronized (this) {
              triggeringPolicy.activateOptions();
              rollingPolicy.activateOptions();
  
              try {
                  RolloverDescription rollover =
                          rollingPolicy.initialize(getFile(), getAppend());
  
                  if (rollover != null) {
                      Action syncAction = rollover.getSynchronous();
  
                      if (syncAction != null) {
                          syncAction.execute();
                      }
  
                      setFile(rollover.getActiveFileName());
                      setAppend(rollover.getAppend());
                      lastRolloverAsyncAction = rollover.getAsynchronous();
  
                      if (lastRolloverAsyncAction != null) {
                          Thread runner = new Thread(lastRolloverAsyncAction);
                          runner.start();
                      }
                  }
  
                  File activeFile = new File(getFile());
  
                  if (getAppend()) {
                      fileLength = activeFile.length();
                  } else {
                      fileLength = 0;
                  }
  
                  super.activateOptions();
              } catch (Exception ex) {
                  exception = ex;
              }
          }
  
          if (exception != null) {
              LogLog.warn(
                      "Exception while initializing RollingFileAppender named '" + getName()
                              + "'", exception);
          }
      }
docs: Prepare instance of use.