Documentation of 'com.udojava.evalex.Expression' Java class
Expression
Skip navigation links
com.udojava.evalex

Class Expression


  • public class Expression
extends java.lang.Object

    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 smallest of the given expressions
    MAX(e1,e2, ...) Returns the biggest of the given 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
    LOG10(expression) Returns the common logarithm (base 10) of an expression
    EXP(expression) Returns Euler's number e raised to the power of a double value.
    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)
    ASIN(expression) Returns the angle of asin (in degrees)
    ACOS(expression) Returns the angle of acos (in degrees)
    ATAN(expression) Returns the angle of atan (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.
    A -1 as the number of parameters denotes a variable number of arguments.
    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)

    • Field Summary

      Fields 
      Modifier and Type Field and Description
      static java.math.BigDecimal PI
      Definition of PI as a constant, can be used in expressions as variable.

    • Constructor Summary

      Constructors 
      Constructor and Description
      Expression(java.lang.String expression)
      Creates a new expression instance from an expression string with a given default match context of MathContext.DECIMAL32.
      Expression(java.lang.String expression, java.math.MathContext defaultMathContext)
      Creates a new expression instance from an expression string with a given default match context.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method and Description
      Expression.Function addFunction(Expression.Function function)
      Adds a function to the list of supported functions
      Expression.Operator addOperator(Expression.Operator operator)
      Adds an operator to the list of supported operators.
      Expression and(java.lang.String variable, java.math.BigDecimal value)
      Sets a variable value.
      Expression and(java.lang.String variable, java.lang.String value)
      Sets a variable value.
      java.math.BigDecimal eval()
      Evaluates the expression.
      java.util.Iterator<java.lang.String> getExpressionTokenizer()
      Get an iterator for this expression, allows iterating over an expression token by token.
      Expression setPrecision(int precision)
      Sets the precision for expression evaluation.
      Expression setRoundingMode(java.math.RoundingMode roundingMode)
      Sets the rounding mode for expression evaluation.
      Expression setVariable(java.lang.String variable, java.math.BigDecimal value)
      Sets a variable value.
      Expression setVariable(java.lang.String variable, java.lang.String value)
      Sets a variable value.
      java.lang.String toRPN()
      Get a string representation of the RPN (Reverse Polish Notation) for this expression.
      Expression with(java.lang.String variable, java.math.BigDecimal value)
      Sets a variable value.
      Expression with(java.lang.String variable, java.lang.String value)
      Sets a variable value.

      • Methods inherited from class java.lang.Object

        equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Field Detail

      • PI

        public static final java.math.BigDecimal PI
        Definition of PI as a constant, can be used in expressions as variable.

    • Constructor Detail

      • Expression

        public Expression(java.lang.String expression)
        Creates a new expression instance from an expression string with a given default match context of MathContext.DECIMAL32.
        Parameters:
        expression - The expression. E.g. "2.4*sin(3)/(2-4)" or "sin(y)>0 & max(z, 3)>3"

      • Expression

        public Expression(java.lang.String expression,
                  java.math.MathContext defaultMathContext)
        Creates a new expression instance from an expression string with a given default match context.
        Parameters:
        expression - The expression. E.g. "2.4*sin(3)/(2-4)" or "sin(y)>0 & max(z, 3)>3"
        defaultMathContext - The MathContext to use by default.

    • Method Detail

      • eval

        public java.math.BigDecimal eval()
        Evaluates the expression.
        Returns:
        The result of the expression.

      • setPrecision

        public Expression setPrecision(int precision)
        Sets the precision for expression evaluation.
        Parameters:
        precision - The new precision.
        Returns:
        The expression, allows to chain methods.

      • setRoundingMode

        public Expression setRoundingMode(java.math.RoundingMode roundingMode)
        Sets the rounding mode for expression evaluation.
        Parameters:
        roundingMode - The new rounding mode.
        Returns:
        The expression, allows to chain methods.

      • addOperator

        public Expression.Operator addOperator(Expression.Operator operator)
        Adds an operator to the list of supported operators.
        Parameters:
        operator - The operator to add.
        Returns:
        The previous operator with that name, or null if there was none.

      • addFunction

        public Expression.Function addFunction(Expression.Function function)
        Adds a function to the list of supported functions
        Parameters:
        function - The function to add.
        Returns:
        The previous operator with that name, or null if there was none.

      • setVariable

        public Expression setVariable(java.lang.String variable,
                              java.math.BigDecimal value)
        Sets a variable value.
        Parameters:
        variable - The variable name.
        value - The variable value.
        Returns:
        The expression, allows to chain methods.

      • setVariable

        public Expression setVariable(java.lang.String variable,
                              java.lang.String value)
        Sets a variable value.
        Parameters:
        variable - The variable to set.
        value - The variable value.
        Returns:
        The expression, allows to chain methods.

      • with

        public Expression with(java.lang.String variable,
                       java.math.BigDecimal value)
        Sets a variable value.
        Parameters:
        variable - The variable to set.
        value - The variable value.
        Returns:
        The expression, allows to chain methods.

      • and

        public Expression and(java.lang.String variable,
                      java.lang.String value)
        Sets a variable value.
        Parameters:
        variable - The variable to set.
        value - The variable value.
        Returns:
        The expression, allows to chain methods.

      • and

        public Expression and(java.lang.String variable,
                      java.math.BigDecimal value)
        Sets a variable value.
        Parameters:
        variable - The variable to set.
        value - The variable value.
        Returns:
        The expression, allows to chain methods.

      • with

        public Expression with(java.lang.String variable,
                       java.lang.String value)
        Sets a variable value.
        Parameters:
        variable - The variable to set.
        value - The variable value.
        Returns:
        The expression, allows to chain methods.

      • getExpressionTokenizer

        public java.util.Iterator<java.lang.String> getExpressionTokenizer()
        Get an iterator for this expression, allows iterating over an expression token by token.
        Returns:
        A new iterator instance for this expression.

      • toRPN

        public java.lang.String toRPN()
        Get a string representation of the RPN (Reverse Polish Notation) for this expression.
        Returns:
        A string with the RPN representation for this expression.
Skip navigation links

DataMelt 3.0 © DataMelt by jWork.ORG

Ads help maintain this website.