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(x<7 || sqrt(max(x,9)) <= 3))").with("x","22.9").eval();
 
 result = new Expression("log10(100)").eval();

Supported Operators

Supported Functions

Supported Constants

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.Functionand 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<BigDecimal> parameters) {
        BigDecimal sum = parameters.get(0).add(parameters.get(1)).add(parameters.get(2));
        return sum.divide(new BigDecimal(3));
    }
});

e.eval(); // returns 16

Project Layout

The software was created and tested using Java 1.6.0.

src/   The Java sources
tests/ JUnit tests

Author and License

Copyright 2012 by Udo Klimaschewski

http://about.me/udo.klimaschewski

http://UdoJava.com

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

• The power of operator (^) implementation was copied from Stack Overflow Thanks to Gene Marin
• The SQRT() function implementation was taken from the book The Java Programmers Guide To numerical Computing (Ronald Mak, 2002)