JFormula

JFormula is a Java library for evaluating mathematical expression. It supports the +, -, *, ^, and % operators, boolean expressions, a short expression format (2x+3y), and variables. The evaluation tree is produced by a pluggable parsing system, and evaluation optimization for symbol value changes is provided. It includes a standard library with 17 mathematical functions, can delegate unknown functions or symbols, and can extend or add new libraries dynamically. Many API samples are included. It is multithreaded and JDK 1.1 compliant. (Source: http://freecode.com/)