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Adding source code for article tracked under BAEL-4576 (#10203) 

Co-authored-by: CHANDRAKANT Kumar <kumar.chandrakant@soprabanking.com>
This commit is contained in:
Kumar Chandrakant 2020-10-29 10:41:46 +05:30 committed by GitHub
parent 170ab9123d
commit 0794a1ad1b
17 changed files with 338 additions and 0 deletions
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1
core-java-modules/core-java-functional/README.md Normal file
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## Relevant articles:

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core-java-modules/core-java-functional/pom.xml Normal file
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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>
<artifactId>core-java-functional</artifactId>
<version>0.1.0-SNAPSHOT</version>
<name>core-java-functional</name>
<packaging>jar</packaging>
<parent>
<groupId>com.baeldung.core-java-modules</groupId>
<artifactId>core-java-modules</artifactId>
<version>0.0.1-SNAPSHOT</version>
<relativePath>../</relativePath>
</parent>
</project>

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core-java-modules/core-java-functional/src/main/java/com/baeldung/functional/Currying.java Normal file
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package com.baeldung.functional;
import java.util.function.Function;
public class Currying {
private static Function<Double, Function<Double, Double>> weight = mass -> gravity -> mass * gravity;
private static Function<Double, Double> weightOnEarth = weight.apply(9.81);
private static Function<Double, Double> weightOnMars = weight.apply(3.75);
public static Double weightOnEarth(Double mass) {
return weightOnEarth.apply(mass);
}
public static Double weightOnMars(Double mass) {
return weightOnMars.apply(mass);
}
public static Function<Double, Double> weightOnEarth() {
final double gravity = 9.81;
return mass -> mass * gravity;
}
}

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core-java-modules/core-java-functional/src/main/java/com/baeldung/functional/FirstClassFunctions.java Normal file
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package com.baeldung.functional;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
public class FirstClassFunctions {
public static List<Integer> sortWithoutLambda(List<Integer> numbers) {
Collections.sort(numbers, new Comparator<Integer>() {
@Override
public int compare(Integer n1, Integer n2) {
return n1.compareTo(n2);
}
});
return numbers;
}
public static List<Integer> sortWithLambda(List<Integer> numbers) {
Collections.sort(numbers, (n1, n2) -> n1.compareTo(n2));
return numbers;
}
}

20
core-java-modules/core-java-functional/src/main/java/com/baeldung/functional/FunctionComposition.java Normal file
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package com.baeldung.functional;
import java.util.function.Function;
public class FunctionComposition {
private static Function<Double, Double> log = (value) -> Math.log(value);
private static Function<Double, Double> sqrt = (value) -> Math.sqrt(value);
public static Double logThenSqrt(Double number) {
Function<Double, Double> logThenSqrt = sqrt.compose(log);
return (logThenSqrt.apply(3.14));
}
public static Double sqrtThenLog(Double number) {
Function<Double, Double> sqrtThenLog = sqrt.andThen(log);
return (sqrtThenLog.apply(3.14));
}
}

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core-java-modules/core-java-functional/src/main/java/com/baeldung/functional/ImmutableData.java Normal file
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package com.baeldung.functional;
public class ImmutableData {
private final String someData;
private final AnotherImmutableData anotherImmutableData;
public ImmutableData(final String someData, final AnotherImmutableData anotherImmutableData) {
this.someData = someData;
this.anotherImmutableData = anotherImmutableData;
}
public String getSomeData() {
return someData;
}
public AnotherImmutableData getAnotherImmutableData() {
return anotherImmutableData;
}
public class AnotherImmutableData {
private final Integer someOtherData;
public AnotherImmutableData(final Integer someData) {
this.someOtherData = someData;
}
public Integer getSomeOtherData() {
return someOtherData;
}
}
}

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core-java-modules/core-java-functional/src/main/java/com/baeldung/functional/Monads.java Normal file
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package com.baeldung.functional;
import java.util.Optional;
public class Monads {
public static Optional<Integer> add(Optional<Integer> val1, Optional<Integer> val2) {
return val1.flatMap(first -> val2.flatMap(second -> Optional.of(first + second)));
}
}

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core-java-modules/core-java-functional/src/main/java/com/baeldung/functional/PureFunctions.java Normal file
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package com.baeldung.functional;
import java.util.List;
import java.util.stream.Collectors;
public class PureFunctions {
public static Integer sum(List<Integer> numbers) {
return numbers.stream()
.collect(Collectors.summingInt(Integer::intValue));
}
}

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core-java-modules/core-java-functional/src/main/java/com/baeldung/functional/Recursion.java Normal file
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package com.baeldung.functional;
public class Recursion {
public static Integer headRecursion(Integer number) {
return (number == 1) ? 1 : number * headRecursion(number - 1);
}
public static Integer tailRecursion(Integer number, Integer result) {
return (number == 1) ? result : tailRecursion(number - 1, result * number);
}
}

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core-java-modules/core-java-functional/src/main/java/com/baeldung/functional/ReferentialTransparency.java Normal file
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package com.baeldung.functional;
import java.util.logging.Level;
import java.util.logging.Logger;
public class ReferentialTransparency {
private static Logger logger = Logger.getGlobal();
public void main() {
String data = new SimpleData().setData("Baeldung")
.getData();
logger.log(Level.INFO, new SimpleData().setData("Baeldung")
.getData());
logger.log(Level.INFO, data);
logger.log(Level.INFO, "Baeldung");
}
public class SimpleData {
private Logger logger = Logger.getGlobal();
private String data;
public String getData() {
logger.log(Level.INFO, "Get data called for SimpleData");
return data;
}
public SimpleData setData(String data) {
logger.log(Level.INFO, "Set data called for SimpleData");
this.data = data;
return this;
}
}
}

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core-java-modules/core-java-functional/src/test/java/com/baeldung/functional/CurryingUnitTest.java Normal file
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package com.baeldung.functional;
import static org.junit.jupiter.api.Assertions.assertEquals;
import org.junit.Test;
public class CurryingUnitTest {
@Test
public void testWeightOnEarth() {
assertEquals(588.6, Currying.weightOnEarth(60.0), 0.1);
}
@Test
public void testWeightOnMars() {
assertEquals(225.0, Currying.weightOnMars(60.0), 0.1);
}
}

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core-java-modules/core-java-functional/src/test/java/com/baeldung/functional/FirstClassFunctionsUnitTest.java Normal file
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package com.baeldung.functional;
import static org.junit.jupiter.api.Assertions.assertEquals;
import java.util.Arrays;
import org.junit.Test;
public class FirstClassFunctionsUnitTest {
@Test
public void testSortingWithoutLambda() {
assertEquals(new Integer(8), FirstClassFunctions.sortWithoutLambda(Arrays.asList(new Integer(10), new Integer(8)))
.get(0));
}
@Test
public void testSortingWithLambda() {
assertEquals(new Integer(8), FirstClassFunctions.sortWithLambda(Arrays.asList(new Integer(10), new Integer(8)))
.get(0));
}
}

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core-java-modules/core-java-functional/src/test/java/com/baeldung/functional/FunctionCompositionUnitTest.java Normal file
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package com.baeldung.functional;
import static org.junit.jupiter.api.Assertions.assertEquals;
import org.junit.Test;
public class FunctionCompositionUnitTest {
@Test
public void testLogThenSqrt() {
assertEquals(1.07, FunctionComposition.logThenSqrt(3.14), 0.01);
}
@Test
public void testSqrtThenLog() {
assertEquals(0.57, FunctionComposition.sqrtThenLog(3.14), 0.01);
}
}

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core-java-modules/core-java-functional/src/test/java/com/baeldung/functional/MonadsUnitTest.java Normal file
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package com.baeldung.functional;
import static org.junit.jupiter.api.Assertions.assertEquals;
import java.util.Optional;
import org.junit.Test;
public class MonadsUnitTest {
@Test
public void testOptionalAdd() {
assertEquals(5, Monads.add(Optional.of(new Integer(2)), Optional.of(new Integer(3)))
.get());
}
}

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core-java-modules/core-java-functional/src/test/java/com/baeldung/functional/PureFunctionsUnitTets.java Normal file
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package com.baeldung.functional;
import static org.junit.jupiter.api.Assertions.assertEquals;
import java.util.Arrays;
import org.junit.Test;
public class PureFunctionsUnitTets {
@Test
public void testSortingWithoutLambda() {
assertEquals(new Integer(18), PureFunctions.sum(Arrays.asList(new Integer(10), new Integer(8))));
}
}

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core-java-modules/core-java-functional/src/test/java/com/baeldung/functional/RecursionUnitTest.java Normal file
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package com.baeldung.functional;
import static org.junit.jupiter.api.Assertions.assertEquals;
import org.junit.Test;
public class RecursionUnitTest {
@Test
public void testHeadRecursion() {
assertEquals(120, Recursion.headRecursion(5));
}
@Test
public void testTailRecursion() {
assertEquals(120, Recursion.tailRecursion(5, 1));
}
}

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core-java-modules/pom.xml
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<module>core-java-exceptions-2</module>
<module>core-java-exceptions-3</module>
<module>core-java-function</module>
<module>core-java-functional</module>
<module>core-java-io</module>
<module>core-java-io-2</module>