This is a simple straightforward json parser using a PushbackReader. It is not very difficult. It operates a little bit like XMLStreamreader, which recognizes tokens and maintains the latest state. It is not complete yet. I need to consider a lot more test cases.
Please be aware that JsonReader is stateless. The minimal required information is kept.
If you want to improve this version, develop tests, build upon this version, .. feel free to do so.