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();
Supported Operators
| Mathematical Operators |
|---|
| Operator | Description |
|---|
| + | Additive operator |
| - | Subtraction operator |
| * | Multiplication operator |
| / | Division operator |
| % | Remainder operator (Modulo) |
| ^ | Power operator |
| Boolean Operators* |
|---|
| Operator | Description |
|---|
| = | Equals |
| == | Equals |
| != | Not equals |
| <> | Not equals |
| < | Less than |
| <= | Less than or equal to |
| > | Greater than |
| >= | Greater than or equal to |
| && | Boolean and |
| || | Boolean or |
*Boolean operators result always in a BigDecimal value of 1 or 0 (zero). Any non-zero value is treated as a _true_ value. Boolean _not_ is implemented by a function.
Supported Functions
| Function* | Description |
|---|
| NOT(expression) | Boolean negation, 1 (means true) if the expression is not zero |
| IF(condition,value_if_true,value_if_false) | Returns one value if the condition evaluates to true or the other if it evaluates to false |
| RANDOM() | Produces a random number between 0 and 1 |
| MIN(e1,e2) | Returns the smaller of both expressions |
| MAX(e1,e2) | Returns the bigger of both expressions |
| ABS(expression) | Returns the absolute (non-negative) value of the expression |
| ROUND(expression,precision) | Rounds a value to a certain number of digits, uses the current rounding mode |
| FLOOR(expression) | Rounds the value down to the nearest integer |
| CEILING(expression) | Rounds the value up to the nearest integer |
| LOG(expression) | Returns the natural logarithm (base e) of an expression |
| SQRT(expression) | Returns the square root of an expression |
| SIN(expression) | Returns the trigonometric sine of an angle (in degrees) |
| COS(expression) | Returns the trigonometric cosine of an angle (in degrees) |
| TAN(expression) | Returns the trigonometric tangens of an angle (in degrees) |
| SINH(expression) | Returns the hyperbolic sine of a value |
| COSH(expression) | Returns the hyperbolic cosine of a value |
| TANH(expression) | Returns the hyperbolic tangens of a value |
| RAD(expression) | Converts an angle measured in degrees to an approximately equivalent angle measured in radians |
| DEG(expression) | Converts an angle measured in radians to an approximately equivalent angle measured in degrees |
*Functions names are case insensitive.
Supported Constants
| Constant | Description |
|---|
| PI | The value of PI, exact to 100 digits |
| TRUE | The value one |
| FALSE | The value zero |
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.Function`and 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 parameters) {
BigDecimal sum = parameters.get(0).add(parameters.get(1)).add(parameters.get(2));
return sum.divide(new BigDecimal(3));
}
});
e.eval(); // returns 16
The software is licensed under the MIT Open Source license (see LICENSE file).
- The *power of* operator (^) implementation was copied from [Stack Overflow](http://stackoverflow.com/questions/3579779/how-to-do-a-fractional-power-on-bigdecimal-in-java) Thanks to Gene Marin
- The SQRT() function implementation was taken from the book [The Java Programmers Guide To numerical Computing](http://www.amazon.de/Java-Number-Cruncher-Programmers-Numerical/dp/0130460419) (Ronald Mak, 2002)