How Can I Easily Evaluate Mathematical Expressions in Java?

Evaluate Mathematical Expressions in Java with Ease

Incorporating dynamic formula evaluation into your Java applications can greatly enhance their functionality. This article explores a solution for evaluating math expressions provided by users, allowing you to easily work with complex formulas like "sin (x pi)/2 1".

The Challenge

To evaluate a given mathematical expression, you need a tool that understands mathematical syntax and can perform the necessary computations. There are several libraries available for this purpose.

Solution: exp4j

One highly recommended library is exp4j, which employs Dijkstra's Shunting Yard algorithm for efficient expression evaluation. Its ease of use and small size (around 25KB) make it an ideal choice.

Using exp4j

To use exp4j, create a Calculable object by providing the expression as a string. You can then set the values of any variables involved in the formula using the withVariable method. Finally, call the calculate method to evaluate the expression. Here's an example:

<code class="java">Calculable calc = new ExpressionBuilder("3 * sin(y) - 2 / (x - 2)")
        .withVariable("x", varX)
        .withVariable("y", varY)
        .build();
double result1 = calc.calculate();</code>

For newer versions of exp4j, use the build and evaluate methods:

<code class="java">Expression calc = new ExpressionBuilder("3 * sin(y) - 2 / (x - 2)")
    .variable("x", x)
    .variable("y", y)
    .build();
double result1 = calc.evaluate();</code>

Custom Functions

exp4j also allows you to define custom functions, enabling you to extend its capabilities for specific requirements. Refer to the exp4j documentation for details on custom function implementation.

By utilizing exp4j, you can effortlessly evaluate mathematical expressions in Java, enhancing the versatility of your applications.

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