BAEL-4695 - Evaluating a Math Expression in Java (#10345)

* Added code for checking if a class is abstract or not.

* Renamed test name as per review comments.

* BAEL-4695 - Added code to evaluate math expressions.

* BAEL-4695 - Added test case for math function.

* BAEL-4695 Added consistent examples and entry in parent pom.

* BAEL-4695 - Added more examples

core-java-modules/core-java-lang-math-3/pom.xml

@@ -0,0 +1,35 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-java-lang-math-3</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+    <name>core-java-lang-math-3</name>
+    <parent>
+        <groupId>com.baeldung.core-java-modules</groupId>
+        <artifactId>core-java-modules</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>net.objecthunter</groupId>
+            <artifactId>exp4j</artifactId>
+            <version>0.4.8</version>
+        </dependency>
+
+        <dependency>
+            <groupId>com.fathzer</groupId>
+            <artifactId>javaluator</artifactId>
+            <version>3.0.3</version>
+        </dependency>
+    </dependencies>
+
+
+    <properties>
+
+    </properties>
+
+</project>

core-java-modules/core-java-lang-math-3/src/test/java/com/baeldung/math/evaluate/EvalauteMathExpressionsUnitTest.java

@@ -0,0 +1,91 @@
+package com.baeldung.math.evaluate;
+
+import javax.script.ScriptEngine;
+import javax.script.ScriptEngineManager;
+import javax.script.ScriptException;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import com.fathzer.soft.javaluator.DoubleEvaluator;
+import com.fathzer.soft.javaluator.StaticVariableSet;
+
+import net.objecthunter.exp4j.Expression;
+import net.objecthunter.exp4j.ExpressionBuilder;
+
+public class EvalauteMathExpressionsUnitTest {
+
+    @Test
+    public void givenSimpleExpression_whenCallEvaluateMethod_thenSuccess() {
+        Expression expression = new ExpressionBuilder("3+2").build();
+        double result = expression.evaluate();
+        Assertions.assertEquals(5, result);
+    }
+
+    @Test
+    public void givenTwoVariables_whenCallEvaluateMethod_thenSuccess() {
+        Expression expression = new ExpressionBuilder("3x+2y").variables("x", "y")
+          .build()
+          .setVariable("x", 2)
+          .setVariable("y", 3);
+        double result = expression.evaluate();
+        Assertions.assertEquals(12, result);
+    }
+    
+    @Test
+    public void givenMathFunctions_whenCallEvaluateMethod_thenSuccess() {
+        Expression expression = new ExpressionBuilder("sin(x)*sin(x)+cos(x)*cos(x)").variables("x")
+          .build()
+          .setVariable("x", 0.5);
+        double result = expression.evaluate();
+        Assertions.assertEquals(1, result);
+    }
+
+    @Test
+    public void givenExpression_whenCallEvaluateMethod_thenSuccess() {
+        String expression = "3+2";
+        DoubleEvaluator eval = new DoubleEvaluator();
+        Double result = eval.evaluate(expression);
+        Assertions.assertEquals(5, result);
+    } 
+    
+    @Test
+    public void givenVariables_whenCallEvaluateMethod_thenSuccess() {
+        String expression = "3*x+2*y";
+        DoubleEvaluator eval = new DoubleEvaluator();
+        StaticVariableSet<Double> variables = new StaticVariableSet<Double>();
+        variables.set("x", 2.0);
+        variables.set("y", 3.0);
+        Double result = eval.evaluate(expression, variables);
+        Assertions.assertEquals(12, result);
+    }
+
+    @Test
+    public void givenMathFunction_whenCallEvaluateMethod_thenSuccess() {
+        String expression = "sin(x)*sin(x)+cos(x)*cos(x)";
+        DoubleEvaluator eval = new DoubleEvaluator();
+        StaticVariableSet<Double> variables = new StaticVariableSet<Double>();
+        variables.set("x", 0.5);
+        Double result = eval.evaluate(expression, variables);
+        Assertions.assertEquals(1, result);
+    }
+
+    @Test
+    public void givenJavaScriptingApiAndSimpleExpression_whenCallEvalMethod_thenSuccess() throws ScriptException {
+        ScriptEngineManager scriptEngineManager = new ScriptEngineManager();
+        ScriptEngine scriptEngine = scriptEngineManager.getEngineByName("JavaScript");
+        String expression = "3+2";
+        Integer result = (Integer) scriptEngine.eval(expression);
+        Assertions.assertEquals(5, result);
+    }
+    
+    @Test
+    public void givenJavaScriptingApi_whenCallEvalMethod_thenSuccess() throws ScriptException {
+        ScriptEngineManager scriptEngineManager = new ScriptEngineManager();
+        ScriptEngine scriptEngine = scriptEngineManager.getEngineByName("JavaScript");
+        String expression = "x=2; y=3; 3*x+2*y;";
+        Double result = (Double) scriptEngine.eval(expression);
+        Assertions.assertEquals(12, result);
+    }
+    
+}

core-java-modules/pom.xml

@@ -84,6 +84,7 @@
         <module>core-java-lang-3</module>
         <module>core-java-lang-math</module>
         <module>core-java-lang-math-2</module>
+        <module>core-java-lang-math-3</module>
         <module>core-java-lang-oop-constructors</module>
         <module>core-java-lang-oop-patterns</module>
         <module>core-java-lang-oop-generics</module>