EvalEx - Java Expression Evaluator

Introduction

EvalEx is a handy expression evaluator for Java, that allows to evaluate simple mathematical and boolean expressions.
Key Features:

• Uses BigDecimal for calculation and result
• Single class implementation, very compact
• No dependencies to external libraries
• Precision and rounding mode can be set
• Supports variables
• Standard boolean and mathematical operators
• Standard basic mathematical and boolean functions
• Custom functions and operators can be added at runtime

Examples

  BigDecimal result = null;

  Expression expression = new Expression("1+1/3");
  result = expression.eval():
  expression.setPrecision(2);
  result = expression.eval():

  result = new Expression("(3.4 + -4.1)/2").eval();

  result = new Expression("SQRT(a^2 + b^2").with("a","2.4").and("b","9.253").eval();

  BigDecimal a = new BigDecimal("2.4");
  BigDecimal b = new BigDecimal("9.235");
  result = new Expression("SQRT(a^2 + b^2").with("a",a).and("b",b).eval();

  result = new Expression("2.4/PI").setPrecision(128).setRoundingMode(RoundingMode.UP).eval();

  result = new Expression("random() > 0.5").eval();

  result = new Expression("not(xinvalid input: '<'7 || sqrt(max(x,9)) invalid input: '<'= 3))").with("x","22.9").eval();
 

Supported Operators

Mathematical Operators
Operator	Description
+	Additive operator
-	Subtraction operator
*	Multiplication operator
/	Division operator
%	Remainder operator (Modulo)
^	Power operator

Boolean Operators*
Operator	Description
=	Equals
==	Equals
!=	Not equals
<>	Not equals
<	Less than
<=	Less than or equal to
>	Greater than
>=	Greater than or equal to
&&	Boolean and
||	Boolean or

*Boolean operators result always in a BigDecimal value of 1 or 0 (zero). Any non-zero value is treated as a _true_ value. Boolean _not_ is implemented by a function.

Supported Functions

Function*	Description
NOT(expression)	Boolean negation, 1 (means true) if the expression is not zero
IF(condition,value_if_true,value_if_false)	Returns one value if the condition evaluates to true or the other if it evaluates to false
RANDOM()	Produces a random number between 0 and 1
MIN(e1,e2)	Returns the smaller of both expressions
MAX(e1,e2)	Returns the bigger of both expressions
ABS(expression)	Returns the absolute (non-negative) value of the expression
ROUND(expression,precision)	Rounds a value to a certain number of digits, uses the current rounding mode
FLOOR(expression)	Rounds the value down to the nearest integer
CEILING(expression)	Rounds the value up to the nearest integer
LOG(expression)	Returns the natural logarithm (base e) of an expression
SQRT(expression)	Returns the square root of an expression
SIN(expression)	Returns the trigonometric sine of an angle (in degrees)
COS(expression)	Returns the trigonometric cosine of an angle (in degrees)
TAN(expression)	Returns the trigonometric tangens of an angle (in degrees)
SINH(expression)	Returns the hyperbolic sine of a value
COSH(expression)	Returns the hyperbolic cosine of a value
TANH(expression)	Returns the hyperbolic tangens of a value
RAD(expression)	Converts an angle measured in degrees to an approximately equivalent angle measured in radians
DEG(expression)	Converts an angle measured in radians to an approximately equivalent angle measured in degrees

*Functions names are case insensitive.

Supported Constants

Constant	Description
PI	The value of PI, exact to 100 digits
TRUE	The value one
FALSE	The value zero

Add Custom Operators

Custom operators can be added easily, simply create an instance of `Expression.Operator` and add it to the expression. Parameters are the operator string, its precedence and if it is left associative. The operators `eval()` method will be called with the BigDecimal values of the operands. All existing operators can also be overridden.
For example, add an operator `x >> n`, that moves the decimal point of _x_ _n_ digits to the right:

 Expression e = new Expression("2.1234 >> 2");

 e.addOperator(e.new Operator(">>", 30, true) {
     @Override
     public BigDecimal eval(BigDecimal v1, BigDecimal v2) {
         return v1.movePointRight(v2.toBigInteger().intValue());
     }
 });

 e.eval(); // returns 212.34
 

Add Custom Functions

Adding custom functions is as easy as adding custom operators. Create an instance of `Expression.Function`and add it to the expression. Parameters are the function name and the count of required parameters. The functions `eval()` method will be called with a list of the BigDecimal parameters. All existing functions can also be overridden.
For example, add a function `average(a,b,c)`, that will calculate the average value of a, b and c:

 Expression e = new Expression("2 * average(12,4,8)");

 e.addFunction(e.new Function("average", 3) {
     @Override
     public BigDecimal eval(List parameters) {
         BigDecimal sum = parameters.get(0).add(parameters.get(1)).add(parameters.get(2));
         return sum.divide(new BigDecimal(3));
     }
 });

 e.eval(); // returns 16
 

The software is licensed under the MIT Open Source license (see LICENSE file).

• The *power of* operator (^) implementation was copied from [Stack Overflow](http://stackoverflow.com/questions/3579779/how-to-do-a-fractional-power-on-bigdecimal-in-java) Thanks to Gene Marin
• The SQRT() function implementation was taken from the book [The Java Programmers Guide To numerical Computing](http://www.amazon.de/Java-Number-Cruncher-Programmers-Numerical/dp/0130460419) (Ronald Mak, 2002)