Efficient Math Expression Evaluation in Java

Evaluating mathematical expressions is a common task in Java development. This can be achieved using various methods, each with its advantages and disadvantages.

Introducing exp4j

exp4j is a popular expression evaluator library for Java that utilizes Dijkstra's Shunting Yard algorithm. Its lightweight (around 25KB) and intuitive API make it a suitable choice for many applications.

Using exp4j for Expression Evaluation

To evaluate math expressions using exp4j:

1. Create an ExpressionBuilder instance with the expression as a parameter.
2. If necessary, define custom function names and associate them with corresponding Java methods.
3. Optionally add variables to the expression using the withVariable or variable methods.
4. Build the expression object using build().
5. Evaluate the expression by calling calculate() or evaluate().

Example Code:

// Version 0.4.7 and below
Calculable calc = new ExpressionBuilder("3 * sin(y) - 2 / (x - 2)")
        .withVariable("x", varX)
        .withVariable("y", varY)
        .build()
double result1=calc.calculate();

// Version 0.4.8 and above
Expression calc = new ExpressionBuilder("3 * sin(y) - 2 / (x - 2)")
    .variable("x", x)
    .variable("y", y)
    .build();
double result1 = calc.evaluate();

exp4j also supports custom function definition and evaluation, providing further flexibility.