Formula4J

When an expression such as B = m/h^2 is part of your program and never changes, then you can always implement the expression directly in code. For example, you can define a method that takes m and h as parameters, does the math as ordinary hard-coded statements, and then finally returns the value B as a result. That's easy.

But what happens when the expression isn't known when the program is being written? That's not so easy, because now you need a general expression parser. In the simplest cases, or if you have enough time, you might build such a parser yourself. But you may prefer to use a tool that's already built, tested, and ready to use. Formula4j is such a tool.

The formula4j Java library has three main benefits:

• speed of development - the API has a simple, straightforward design. It can be understood by any member of your team in a very short time.
• accuracy - you avoid all rounding errors associated with floating-point data types. Such rounding errors are unacceptable in a business context.
• security - you avoid system security problems associated with general eval() exploits (a form of code injection). Formula4j parses its input using a grammar strictly limited to mathematical expressions.

Other important facts about formula4j:

• it gives you a JDK 5+ API for the run-time evaluation of basic mathematical expressions
• it targets typical business applications, and not scientific applications
• it lets you use functions and variables in your expressions
• it gives you 48 built-in, commonly used functions
• it lets you define new functions in code
• it lets you define new functions in plain text, so end users can extend your program without coding
• it gives you Decimal, a better abstraction than BigDecimal for most business apps
• it uses UTF-8, so you can use Greek letters such as α, β, and so on, in your expressions
• it lets you change (or translate) the names of its built-in functions
• it depends on javacc 5.0 and junit.jar (3.8.1)
• it includes a simple demo application

What formula4j does not give you:

• no string functions (sorry)
• no deep-level control over its internal parser
• no complex numbers, matrices, fancy-pants abstract algebra, and so on