Implemented FunctionFactory exercise

Author: Taras

.gitignore

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+.idea
+**/*.iml
+**/target

README.md

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+# Java 8 exercises

math-functions-factory/pom.xml

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+<?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">
+    <parent>
+        <artifactId>java-8-exercises</artifactId>
+        <groupId>com.bobocode</groupId>
+        <version>1.0-SNAPSHOT</version>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>math-functions-factory</artifactId>
+
+    <dependencies>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>4.12</version>
+        </dependency>
+    </dependencies>
+
+</project>

math-functions-factory/src/main/java/com.bobocode/FunctionFactory.java

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+package com.bobocode;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.function.Function;
+
+/**
+ * FunctionFactory is an API that allows you to store and retrieve functions by name. Functions are stored in a HashMap,
+ * where the key is a function name, and the value is a Function<T,R> instance. Methods addFunction(), and getFunction()
+ * are already implemented.
+ * <p>
+ * The task is to create different types of functions and manage them using FunctionFactory. The instruction is placed
+ * to the main method.
+ */
+public class FunctionFactory<T, R> {
+    private Map<String, Function<T, R>> functionMap;
+
+    private FunctionFactory() {
+        functionMap = new HashMap<>();
+    }
+
+    public static FunctionFactory<Integer, Integer> integerFunctionFactory(){
+        return new FunctionFactory<>();
+    }
+
+    public void addFunction(String name, Function<T, R> function) {
+        functionMap.put(name, function);
+    }
+
+    public Function<T, R> getFunction(String name) {
+        if (functionMap.containsKey(name)) {
+            return functionMap.get(name);
+        } else {
+            throw new InvalidFunctionNameException(name);
+        }
+    }
+}

math-functions-factory/src/main/java/com.bobocode/InvalidFunctionNameException.java

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+package com.bobocode;
+
+public class InvalidFunctionNameException extends RuntimeException {
+    public InvalidFunctionNameException(String functionName) {
+        super("Function " + functionName + " doesn't exist.");
+    }
+}

math-functions-factory/src/test/java/com/bobocode/FunctionFactoryTest.java

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+package com.bobocode;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+import java.util.function.Function;
+
+import static org.junit.Assert.assertEquals;
+
+@RunWith(JUnit4.class)
+public class FunctionFactoryTest {
+    private FunctionFactory<Integer, Integer> integerFunctionFactory =  FunctionFactory.integerFunctionFactory();
+
+    @Test
+    public void testAddSquareFunction(){
+        integerFunctionFactory.addFunction("square", n -> n * n);
+
+        Function<Integer, Integer> square = integerFunctionFactory.getFunction("square");
+        assertEquals(25, square.apply(5).intValue());
+    }
+}

pom.xml

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+<?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>
+
+    <groupId>com.bobocode</groupId>
+    <artifactId>java-8-exercises</artifactId>
+    <packaging>pom</packaging>
+    <version>1.0-SNAPSHOT</version>
+    <modules>
+        <module>math-functions-factory</module>
+    </modules>
+
+    <properties>
+        <maven.compiler.source>1.8</maven.compiler.source>
+        <maven.compiler.target>1.8</maven.compiler.target>
+    </properties>
+
+</project>