Java-Calculator

This is simple calculator in Java, evaluates also logical expressions; all the arithemtic operations are make on Java BigDecials and BigIntegers; logical operations are on Booleans. Usage:
Always feed prompt with fully paranthesized expressions: ((2 + 2) -2.01), ~(t -> t) && ~f). Propositional Calculus Evaluation: use t as a true, f as a false; ~ - for negation, && - for and, || for or, -> for implictaion.
Main method in Calculator class.
Info also on: https://lion137.blogspot.co.uk/2017/06/calculator.html