Added toOptional method and unit tests

src/main/java/com/ceticamarco/lambdatonic/Either.java

@@ -1,5 +1,6 @@
 package com.ceticamarco.lambdatonic;
 
+import java.util.Optional;
 import java.util.function.Function;
 
 /**
@@ -99,4 +100,13 @@ public sealed interface Either<L, R> permits Left, Right {
      */
     L fromLeft(L defaultValue);
 
+    /**
+     * <p>
+     *     Converts an <i>Either</i> data type to a <i>java.util.Optional</i>.
+     *     The <i>Right</i> becomes a non-null <i>Optional</i> and the <i>Left</i>
+     *     becomes a null <i>Optional</i>
+     * </p>
+     * @return An <i>Optional</i> data type
+     */
+    Optional<R> toOptional();
 }

src/main/java/com/ceticamarco/lambdatonic/Left.java

@@ -1,5 +1,6 @@
 package com.ceticamarco.lambdatonic;
 
+import java.util.Optional;
 import java.util.function.Function;
 
 /**
@@ -46,4 +47,9 @@ public record Left<L, R>(L value) implements Either<L, R> {
     public L fromLeft(L defaultValue) {
         return this.value;
     }
+
+    @Override
+    public Optional<R> toOptional() {
+        return Optional.empty();
+    }
 }

src/main/java/com/ceticamarco/lambdatonic/Right.java

@@ -1,5 +1,6 @@
 package com.ceticamarco.lambdatonic;
 
+import java.util.Optional;
 import java.util.function.Function;
 
 /**
@@ -46,4 +47,9 @@ public record Right<L, R>(R value) implements Either<L, R> {
     public L fromLeft(L defaultValue) {
         return defaultValue;
     }
+
+    @Override
+    public Optional<R> toOptional() {
+        return Optional.of(this.value);
+    }
 }

src/test/java/com/ceticamarco/lambdatonic/LeftTests.java

@@ -3,6 +3,7 @@ package com.ceticamarco.lambdatonic;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.BeforeEach;
 
+import java.util.Optional;
 import java.util.function.Function;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
@@ -94,4 +95,12 @@ public class LeftTests {
     public void testFromLeftOnLeft() {
         assertEquals(this.resEither.fromLeft(-1), 19);
     }
+
+    @Test
+    public void testToOptionalFromLeft() {
+        assertEquals(
+            this.numEither.toOptional(),
+            Optional.empty()
+        );
+    }
 }

src/test/java/com/ceticamarco/lambdatonic/RightTests.java

@@ -3,6 +3,7 @@ package com.ceticamarco.lambdatonic;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.BeforeEach;
 
+import java.util.Optional;
 import java.util.function.Function;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
@@ -94,4 +95,12 @@ public class RightTests {
     public void testFromLeftOnRight() {
         assertEquals(this.resEither.fromLeft(-1), -1);
     }
+
+    @Test
+    public void testToOptionalFromRight() {
+        assertEquals(
+            this.numEither.toOptional(),
+            Optional.of(4)
+        );
+    }
 }