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thibault.faure
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BAEL-5725 code for the TriFunction interface article
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‎core-java-modules/core-java-function/pom.xml‎

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<artifactId>core-java-function</artifactId>
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<version>0.1.0-SNAPSHOT</version>
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<version>${mockito-inline.version}</version>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>io.vavr</groupId>
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<artifactId>vavr</artifactId>
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<version>${vavr.version}</version>
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</dependency>
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</dependencies>
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<build>
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<mockito-inline.version>3.8.0</mockito-inline.version>
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<assertj.version>3.22.0</assertj.version>
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<commons-lang3.version>3.12.0</commons-lang3.version>
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<vavr.version>0.10.4</vavr.version>
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</properties>
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</project>

‎core-java-modules/core-java-function/src/main/java/com/baeldung/trifunction/TriFunction.java‎

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package com.baeldung.trifunction;
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import java.util.Objects;
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import java.util.function.Function;
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/**
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* Represents a function that accepts three arguments and produces a result.
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* This is the three-arity specialization of {@link Function}.
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*
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* <p>This is a functional interface
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* whose functional method is {@link #apply(Object, Object, Object)}.
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*
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* @param <T> the type of the first argument to the function
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* @param <U> the type of the second argument to the function
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* @param <V> the type of the third argument to the function
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* @param <R> the type of the result of the function
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*
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* @see Function
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*/
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@FunctionalInterface
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public interface TriFunction<T, U, V, R> {
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/**
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* Applies this function to the given arguments.
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*
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* @param t the first function argument
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* @param u the second function argument
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* @param v the third function argument
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* @return the function result
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*/
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R apply(T t, U u, V v);
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/**
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* Returns a composed function that first applies this function to
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* its input, and then applies the {@code after} function to the result.
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* If evaluation of either function throws an exception, it is relayed to
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* the caller of the composed function.
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*
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* @param <K> the type of output of the {@code after} function, and of the
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* composed function
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* @param after the function to apply after this function is applied
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* @return a composed function that first applies this function and then
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* applies the {@code after} function
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* @throws NullPointerException if after is null
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*/
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default <K> TriFunction<T, U, V, K> andThen(Function<? super R, ? extends K> after) {
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Objects.requireNonNull(after);
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return (T t, U u, V v) -> after.apply(apply(t, u, v));
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}
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}

‎core-java-modules/core-java-function/src/main/java/com/baeldung/trifunction/TriFunctionExample.java‎

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package com.baeldung.trifunction;
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public class TriFunctionExample {
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public static TriFunction<Integer, Integer, Integer, Integer> multiplyThenAdd = (x, y, z) -> x * y + z;
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public static TriFunction<Integer, Integer, Integer, Integer> multiplyThenAddThenDivideByTen = multiplyThenAdd.andThen(x -> x / 10);
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public static TriFunction<Integer, String, Boolean, String> convertIntegerOrReturnStringDependingOnCondition = (myInt, myStr, myBool) -> {
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if (Boolean.TRUE.equals(myBool)) {
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return myInt != null ? myInt.toString() : "";
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} else {
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return myStr;
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}
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};
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}

‎core-java-modules/core-java-function/src/main/java/com/baeldung/trifunction/VavrFunction3Example.java‎

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package com.baeldung.trifunction;
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import io.vavr.Function3;
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public class VavrFunction3Example {
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public static Function3<Integer, Integer, Integer, Integer> multiplyThenAdd = (x, y, z) -> x * y + z;
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public static Function3<Integer, Integer, Integer, Integer> multiplyThenAddThenDivideByTen = multiplyThenAdd.andThen(x -> x / 10);
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}

‎core-java-modules/core-java-function/src/test/java/com/baeldung/trifunction/TriFunctionExampleUnitTest.java‎

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package com.baeldung.trifunction;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import org.junit.jupiter.api.Test;
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class TriFunctionExampleUnitTest {
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private static final String BAELDUNG = "baeldung";
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@Test
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void whenMultiplyThenAdd_ThenReturnsCorrectResult() {
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assertEquals(25, TriFunctionExample.multiplyThenAdd.apply(2, 10, 5));
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}
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@Test
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void whenMultiplyThenAddThenDivideByTen_ThenReturnsCorrectResult() {
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assertEquals(2, TriFunctionExample.multiplyThenAddThenDivideByTen.apply(2, 10, 5));
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}
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@Test
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void givenTrueBooleanAndNullInteger_WhenConvertIntegerOrReturnStringDependingOnCondition_ThenEmptyString() {
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assertEquals("", TriFunctionExample.convertIntegerOrReturnStringDependingOnCondition.apply(null, BAELDUNG, true));
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}
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@Test
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void givenTrueBooleanAndNonNullInteger_WhenConvertIntegerOrReturnStringDependingOnCondition_ThenConvertIntegerToString() {
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assertEquals("88", TriFunctionExample.convertIntegerOrReturnStringDependingOnCondition.apply(88, BAELDUNG, true));
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}
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@Test
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void givenFalseBoolean_WhenConvertIntegerOrReturnStringDependingOnCondition_ThenReturnTheString() {
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assertEquals(BAELDUNG, TriFunctionExample.convertIntegerOrReturnStringDependingOnCondition.apply(null, BAELDUNG, false));
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}
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@Test
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void givenNullBoolean_WhenConvertIntegerOrReturnStringDependingOnCondition_ThenReturnTheString() {
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assertEquals(BAELDUNG, TriFunctionExample.convertIntegerOrReturnStringDependingOnCondition.apply(null, BAELDUNG, null));
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}
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}

‎core-java-modules/core-java-function/src/test/java/com/baeldung/trifunction/VavrFunction3ExampleUnitTest.java‎

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package com.baeldung.trifunction;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import org.junit.jupiter.api.Test;
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public class VavrFunction3ExampleUnitTest {
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@Test
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void whenMultiplyThenAdd_ThenReturnsCorrectResult() {
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assertEquals(25, VavrFunction3Example.multiplyThenAdd.apply(2, 10, 5));
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}
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@Test
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void whenMultiplyThenAddThenDivideByTen_ThenReturnsCorrectResult() {
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assertEquals(2, VavrFunction3Example.multiplyThenAddThenDivideByTen.apply(2, 10, 5));
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}
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}

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