There seems to be a bug in outputting a HarLog object to a string. After successfully loading a valid HAR file into a HarLog object using the toString method outputs an invalid HAR. This is seen using 1.0.1 and 1.1.
HarFileReader reader = new HarFileReader();
HarLog log = reader.readHarFile(new File("path/to/file"));
See attached HAR file generated by Chrome for the Google home page.