Exp4j

exp4j is a small Java library for evaluation of mathematical expressions.¹ It implements Dijkstra's Shunting-yard algorithm to translate expressions from infix notation to Reverse Polish notation and calculates the result using a simple Stack algorithm.

• Variables can be used in expressions
• exp4j comes with a set of common built-in functions
• Users can create and use their own custom operators
• Users can create and use their own custom functions

exp4j is released under the terms of the Apache License 2.0

Calculating the result of ${\displaystyle 3*{\frac {\sin {(\pi )}-2}{e}}}$ can be done in the following way:

Expression e = new ExpressionBuilder("3 * (sin(pi) - 2 )/ e")
        .variables("pi", "e")
        .build()
        .setVariable("pi", Math.PI)
        .setVariable("e", Math.E);
double result = e.evaluate();