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me4j

Java library for parsing and evaluating mathematical expression strings

Usage

There are two interfaces to the me4j API: Expression and MathEvaluator. Current functionality is identical between the two, but the Expression class has been included to support variables and additional functionality in the future. The MathEvaluator class is a static utility class intended for one-shot evaluation.

To evaluate a String using an Expression, create a new instance by passing the expression string, and call evaluate() on the new instance:

Expression myExpression = new Expression ("1 + 1");
double shouldBeTwo = myExpression.evaluate ();

To evaluate a String using the MathEvaluator class, call the static evaluate() method and pass in the string. In the background, the MathEvaluator class is performing the same operation as above.

double shouldBeTwo = MathEvaluator.evaluate ("1 + 1");

Supported Operator Symbols

Operations

  • Addition ("+")
  • Subtraction ("-")
  • Multiplication ("*")
  • Division ("/")
  • Exponentiation ("^")

Grouping

  • Parentheses ("()")
  • Square Brackets ("[]")
  • Curly Brackets ("{}")

Formatting

The latest revision (4/19/14) removes the whitespace delimiter requirement, so any string, with or without whitespace, should be properly parsed.

Future Plans

In no particular order

  • Add support for parsing operands written in scientific notation
  • Unary operators, such as negation ( - ) and factorial ( ! ) -- in progress
  • Support common functions like sine/cosine/tangent
  • Support custom functions
  • Support variables (operands whose values can be defined after parsing)
  • Support expression reusability (similar to java.sql.PreparedStatement)