BAEL-5725 code for the TriFunction interface article

core-java-modules/core-java-function/pom.xml

@@ -1,7 +1,7 @@
 <?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">
+         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-function</artifactId>
     <version>0.1.0-SNAPSHOT</version>
@@ -32,6 +32,11 @@
             <version>${mockito-inline.version}</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>io.vavr</groupId>
+            <artifactId>vavr</artifactId>
+            <version>${vavr.version}</version>
+        </dependency>
     </dependencies>
 
     <build>
@@ -48,6 +53,7 @@
         <mockito-inline.version>3.8.0</mockito-inline.version>
         <assertj.version>3.22.0</assertj.version>
         <commons-lang3.version>3.12.0</commons-lang3.version>
+        <vavr.version>0.10.4</vavr.version>
     </properties>
 
 </project>

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

@@ -0,0 +1,50 @@
+package com.baeldung.trifunction;
+
+import java.util.Objects;
+import java.util.function.Function;
+
+/**
+ * Represents a function that accepts three arguments and produces a result.
+ * This is the three-arity specialization of {@link Function}.
+ *
+ * <p>This is a functional interface
+ * whose functional method is {@link #apply(Object, Object, Object)}.
+ *
+ * @param <T> the type of the first argument to the function
+ * @param <U> the type of the second argument to the function
+ * @param <V> the type of the third argument to the function
+ * @param <R> the type of the result of the function
+ *
+ * @see Function
+ */
+@FunctionalInterface
+public interface TriFunction<T, U, V, R> {
+
+    /**
+     * Applies this function to the given arguments.
+     *
+     * @param t the first function argument
+     * @param u the second function argument
+     * @param v the third function argument
+     * @return the function result
+     */
+    R apply(T t, U u, V v);
+
+    /**
+     * Returns a composed function that first applies this function to
+     * its input, and then applies the {@code after} function to the result.
+     * If evaluation of either function throws an exception, it is relayed to
+     * the caller of the composed function.
+     *
+     * @param <K> the type of output of the {@code after} function, and of the
+     *           composed function
+     * @param after the function to apply after this function is applied
+     * @return a composed function that first applies this function and then
+     * applies the {@code after} function
+     * @throws NullPointerException if after is null
+     */
+    default <K> TriFunction<T, U, V, K> andThen(Function<? super R, ? extends K> after) {
+        Objects.requireNonNull(after);
+        return (T t, U u, V v) -> after.apply(apply(t, u, v));
+    }
+}

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

@@ -0,0 +1,17 @@
+package com.baeldung.trifunction;
+
+public class TriFunctionExample {
+
+    public static TriFunction<Integer, Integer, Integer, Integer> multiplyThenAdd = (x, y, z) -> x * y + z;
+
+    public static TriFunction<Integer, Integer, Integer, Integer> multiplyThenAddThenDivideByTen = multiplyThenAdd.andThen(x -> x / 10);
+
+    public static TriFunction<Integer, String, Boolean, String> convertIntegerOrReturnStringDependingOnCondition = (myInt, myStr, myBool) -> {
+        if (Boolean.TRUE.equals(myBool)) {
+            return myInt != null ? myInt.toString() : "";
+        } else {
+            return myStr;
+        }
+    };
+
+}

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

@@ -0,0 +1,11 @@
+package com.baeldung.trifunction;
+
+import io.vavr.Function3;
+
+public class VavrFunction3Example {
+
+    public static Function3<Integer, Integer, Integer, Integer> multiplyThenAdd = (x, y, z) -> x * y + z;
+
+    public static Function3<Integer, Integer, Integer, Integer> multiplyThenAddThenDivideByTen = multiplyThenAdd.andThen(x -> x / 10);
+
+}

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

@@ -0,0 +1,41 @@
+package com.baeldung.trifunction;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+class TriFunctionExampleUnitTest {
+
+    private static final String BAELDUNG = "baeldung";
+
+    @Test
+    void whenMultiplyThenAdd_ThenReturnsCorrectResult() {
+        assertEquals(25, TriFunctionExample.multiplyThenAdd.apply(2, 10, 5));
+    }
+
+    @Test
+    void whenMultiplyThenAddThenDivideByTen_ThenReturnsCorrectResult() {
+        assertEquals(2, TriFunctionExample.multiplyThenAddThenDivideByTen.apply(2, 10, 5));
+    }
+
+    @Test
+    void givenTrueBooleanAndNullInteger_WhenConvertIntegerOrReturnStringDependingOnCondition_ThenEmptyString() {
+        assertEquals("", TriFunctionExample.convertIntegerOrReturnStringDependingOnCondition.apply(null, BAELDUNG, true));
+    }
+
+    @Test
+    void givenTrueBooleanAndNonNullInteger_WhenConvertIntegerOrReturnStringDependingOnCondition_ThenConvertIntegerToString() {
+        assertEquals("88", TriFunctionExample.convertIntegerOrReturnStringDependingOnCondition.apply(88, BAELDUNG, true));
+    }
+
+    @Test
+    void givenFalseBoolean_WhenConvertIntegerOrReturnStringDependingOnCondition_ThenReturnTheString() {
+        assertEquals(BAELDUNG, TriFunctionExample.convertIntegerOrReturnStringDependingOnCondition.apply(null, BAELDUNG, false));
+    }
+
+    @Test
+    void givenNullBoolean_WhenConvertIntegerOrReturnStringDependingOnCondition_ThenReturnTheString() {
+        assertEquals(BAELDUNG, TriFunctionExample.convertIntegerOrReturnStringDependingOnCondition.apply(null, BAELDUNG, null));
+    }
+
+}

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

@@ -0,0 +1,19 @@
+package com.baeldung.trifunction;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class VavrFunction3ExampleUnitTest {
+
+    @Test
+    void whenMultiplyThenAdd_ThenReturnsCorrectResult() {
+        assertEquals(25, VavrFunction3Example.multiplyThenAdd.apply(2, 10, 5));
+    }
+
+    @Test
+    void whenMultiplyThenAddThenDivideByTen_ThenReturnsCorrectResult() {
+        assertEquals(2, VavrFunction3Example.multiplyThenAddThenDivideByTen.apply(2, 10, 5));
+    }
+
+}