BAEL-5725 code for the TriFunction interface article

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);
+
+}