JBEE - Java Basic Expression Evaluator (library)

JBEE is yet another parser and evaluator for arithmetic expressions. It started out as a calculator component for TradeTrax, but quickly matured into a standalone project.

Why another EE library? Because writing one from scratch was faster/easier than dealing with the bugs/shortcomings of existing libraries:

Open Source License

JBEE is licensed under the terms of the APL 2.

Self contained

An expression parser already is a dependency. It should not add dependencies of it's own to any project.

Arbitrary precision calculation

An EE library must be suitable for doing financial calculations without precession loss. That is, use java.math.BigDecimal exclusively (surprisingly many EE libs get this wrong and use Java primitive types instead).

Honor the user's Locale settings

Depending on the locale, the result of 1/4 is either written as 0.25 or 0,25 (likewise, 10^3 may be written as 1,000 or 1.000) depending on the Locale. No other EE lib supports this.

Correctness

Getting precedence right with infix notation is notoriously difficult. Any parser that's not based on a formal (YACC) grammar is potentially doing it wrong (unit tests do not substitute for proving correctness)!

Using JBEE

Using JBEE is as simple as it gets:

// Use default locale and MathLib
Evaluator e = new Evaluator();
BigDecimal result = e.evaluate("3,000 * 4.0 + 0xFF");
System.out.println(result);