Looking for an expression evaluator

Question

I\'m looking for an evaluator for simple condition expressions. Expressions should include variables (read only), strings, numbers and some basic operators.

E.g. exp

Answer 1

Why don't you use Rhino? It's a JavaScript engine already present inside the JDK.

It can evaluate whatever you like to write in JS.. take a look here

Answer 2

What about SPEL (Spring Expression Lang); http://static.springsource.org/spring/docs/3.0.x/reference/expressions.html

Answer 3

This simple recursive descent parser evaluates constants as named functions having no parameters.

Answer 4

Here is a little library I've worked on that supports expression evaluation (including variables, strings, boolean, etc...).

A little example :

String expression = "EXP(var)";
ExpressionEvaluator evaluator = new ExpressionEvaluator();
evaluator.putVariable(new Variable("var", VariableType.NUMBER, new BigDecimal(20)));

System.out.println("Value of exp(var) : " + evaluator.evaluate(expression).getValue());

Answer 5

Sounds like JEXL might work well for you. Check out its syntax reference.

Answer 6

A very simple and easy to use alternative with a lot of built in excel functions for string, date and number formatting.

The library also allows easy addition of custom functions. A lot of examples available on the git page. A simple example using variables

  ExpressionsEvaluator evalExpr = ExpressionsFactory.create("LEFT(City, 3)");
  Map<String, Object> variables = new HashMap<String, Object>();
  variables.put("City", "New York");
  assertEquals("New", evalExpr.eval(variables));