InputStreamReader, FileInputStream starts parsing file at midpoint instead of beginning

Question

I'm attempting to parse a UTF 16 encoded JSON file, however I've run into a weird issue.

Whenever I use a FileInputStream, parsing the file seems to start at the midpoint. For example, if the file is 40 characters long, it will begin at character 20. This causes errors with parsing the JSON, as obviously its data begins at character 0 in the file.

This issue cropped up the other day, despite working for weeks. I can see no issue with my code as it wasn't changed in the days leading up to the issue starting.

One of my attempted workarounds was to switch to using a FileReader. It begins normally at character zero, however it cannot handle the UTF-16 characters in the document, so does not solve the problem.

I am using Google's Gson library for handling JSON, however I think the issue lies somewhere within the InputStreamReader, or with FileInputStream.

Below is the code which is at issue;

JsonReader reader = new JsonReader(new InputStreamReader(new FileInputStream(file), "UTF-16"));
reader.beginArray();
...

Here is the error it throws. The line reader.beginArray(); above causes the exception.

java.lang.IllegalStateException: Expected BEGIN_ARRAY but was STRING at line 1 column 21
    at com.google.gson.stream.JsonReader.expect(JsonReader.java:337)
    at com.google.gson.stream.JsonReader.beginArray(JsonReader.java:304)
    at reader.ProofDatabase.load(ProofDatabase.java:130)
    ...

And here is my partial workaround which does not handle UTF16 strings

JsonReader reader = new JsonReader(new FileReader(file));
reader.beginArray();
...

Any solution, be it a fix to the original problem, or another method of reading in the file as UTF-16 would be more than welcome.

Answer 1

Forgot to update the question when I found the solution.

The error came from the fact that I manually created the JSON file rather than programmatically generating it.

When the file was generated by the JSONWriter class, extra meta-data was added to the file that told the parser that it was a JSON file. This meta-data was missing in the manually created file, so JSONReader was throwing errors in parsing the file.