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)