Basic.java must contain main.

- There must be only one argument (args) and if there are none or more than 1, an error message must be printed and the program exits

- That one argument will be considered a filename

- Use File.ReadAllLines to read all of the lines from the file that is denoted by filename

- Instantiate one instance of your Lexer class for each line from ReadAllLines

- Parse each line using the lex method of the Lexer class

- Take the list of tokens from lex and concatenate it to a single list. If lex throws an exception you must catch the exception, print that there was an exception, and lex the next line

- Print each token out once the lexing is complete