docs: public int getApproximateLength() {
      if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.entry(this, tc, "getApproximateLength");
  
      if (approxLength == -1) approxLength = guessApproxLength();
  
      if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.exit(this, tc, "getApproximateLength", Integer.valueOf(approxLength));
      return approxLength;
    }