EvalEx - Java Expression Evaluator

EvalEx is a handy expression evaluator for Java, that allows to parse and evaluate expression strings.

Key Features:

• Supports numerical, boolean, string, array and structure expressions, operations and variables.
• Array and structure support: Arrays and structures can be mixed, building arbitrary data structures.
• Uses BigDecimal for numerical calculations.
• MathContext and number of decimal places can be configured, with optional automatic rounding.
• No dependencies to external libraries.
• Easy integration into existing systems to access data.
• Predefined boolean and mathematical operators.
• Predefined mathematical, boolean and string functions.
• Custom functions and operators can be added.
• Functions can be defined with a variable number of arguments (see MIN, MAX and SUM functions).
• Supports hexadecimal and scientific notations of numbers.
• Supports implicit multiplication, e.g. (a+b)(a-b) or 2(x-y) which equals to (a+b)*(a-b) or 2*( x-y)
• Lazy evaluation of function parameters (see the IF function) and support of sub-expressions.

Documentation

The full documentation for EvalEx can be found on GitHub Pages

Discussion

For announcements, questions and ideas visit the Discussions area.

Examples

A simple example, that shows how it works in general:

Expression expression = new Expression("1 + 2 / (4 * SQRT(4))");

EvaluationValue result = expression.evaluate();

System.out.println(result.getNumberValue()); // prints 1.25

Variables can be specified in the expression and their values can be passed for evaluation:

Expression expression = new Expression("(a + b) * (a - b)");

EvaluationValue result = expression
    .with("a", 3.5)
    .and("b", 2.5)
    .evaluate();

System.out.println(result.getNumberValue()); // prints 6.00

Boolean expressions produce a boolean result:

Expression expression = new Expression("level > 2 || level <= 0");

EvaluationValue result = expression
    .with("level", 3.5)
    .evaluate();

System.out.println(result.getBooleanValue()); // prints true

Like in Java, strings and text can be mixed:

Expression expression = new Expression("\"Hello \" + name + \", you are \" + age")
    .with("name","Frank")
    .and("age",38);

System.out.println(expression.evaluate().getStringValue()); // prints Hello Frank, you are 38

Arrays are supported and can be passed as Java Lists.

See the Documentation for more details.

Expression expression = new Expression("values[i-1] * factors[i-1]");

EvaluationValue result = expression
    .with("values", List.of(2, 3, 4))
    .and("factors", List.of(2, 4, 6))
    .and("i", 1)
    .evaluate();

System.out.println(result.getNumberValue()); // prints 4

Structures are supported and can be passed as Java Maps.

Arrays and Structures can be combined to build arbitrary data structures. See the Documentation for more details.

Map<String, Object> order = new HashMap<>();
order.put("id", 12345);
order.put("name", "Mary");

Map<String, Object> position = new HashMap<>();
position.put("article", 3114);
position.put("amount", 3);
position.put("price", new BigDecimal("14.95"));

order.put("positions", List.of(position));

Expression expression = new Expression("order.positions[x].amount * order.positions[x].price")
    .with("order", order)
    .and("x", 0);

BigDecimal result = expression.evaluate().getNumberValue();

System.out.println(result); // prints 44.85

Author and License

Copyright 2012-2022 by Udo Klimaschewski

Thanks to all who contributed to this project: Contributors

The software is licensed under the Apache License, Version 2.0 ( see LICENSE file).

• The power of operator (^) implementation was copied from Stack Overflow Thanks to Gene Marin