Current Status: Wrong type of file and relative filename implemented.
- Save to a file in specified path by the user.
- Arith expressions working. 
- Bug on EOF expected has been fixed. New line added between evaluated s-expressions.
- JFileChooser Window displaying and properly working. // Code Streamlining to make it more efficient.
- JUnit Tests implemented.
- GUI is printing the results on textarea on clicking the execute button.
- The results are printed to an output file.