diff --git a/lib/src/main/java/com/github/tonivade/vavr/effect/Fiber.java b/lib/src/main/java/com/github/tonivade/vavr/effect/Fiber.java
index 4270cab..d934c88 100644
--- a/lib/src/main/java/com/github/tonivade/vavr/effect/Fiber.java
+++ b/lib/src/main/java/com/github/tonivade/vavr/effect/Fiber.java
@@ -1,25 +1,18 @@
 /*
- * Copyright (c) 2018-2021, Antonio Gabriel Muñoz Conejo <antoniogmc at gmail dot com>
+ * Copyright (c) 2022, Antonio Gabriel Muñoz Conejo <antoniogmc at gmail dot com>
  * Distributed under the terms of the MIT License
  */
 package com.github.tonivade.vavr.effect;
 
-public interface Fiber<T> {
+public sealed interface Fiber<T> {
 
   IO<T> join();
   
   IO<Unit> cancel();
   
   static <T> Fiber<T> of(IO<T> join, IO<Unit> cancel) {
-    return new Fiber<T>() {
-      @Override
-      public IO<T> join() {
-        return join;
-      }
-      @Override
-      public IO<Unit> cancel() {
-        return cancel;
-      }
-    };
+    return new FiberImpl<>(join, cancel);
   }
+  
+  record FiberImpl<T>(IO<T> join, IO<Unit> cancel) implements Fiber<T> {}
 }
\ No newline at end of file
diff --git a/lib/src/main/java/com/github/tonivade/vavr/effect/IO.java b/lib/src/main/java/com/github/tonivade/vavr/effect/IO.java
index ce9ad3c..aa179af 100644
--- a/lib/src/main/java/com/github/tonivade/vavr/effect/IO.java
+++ b/lib/src/main/java/com/github/tonivade/vavr/effect/IO.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2021, Antonio Gabriel Muñoz Conejo <antoniogmc at gmail dot com>
+ * Copyright (c) 2022, Antonio Gabriel Muñoz Conejo <antoniogmc at gmail dot com>
  * Distributed under the terms of the MIT License
  */
 package com.github.tonivade.vavr.effect;
diff --git a/lib/src/main/java/com/github/tonivade/vavr/effect/Ref.java b/lib/src/main/java/com/github/tonivade/vavr/effect/Ref.java
index 175ece3..5dd2abf 100644
--- a/lib/src/main/java/com/github/tonivade/vavr/effect/Ref.java
+++ b/lib/src/main/java/com/github/tonivade/vavr/effect/Ref.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2021, Antonio Gabriel Muñoz Conejo <antoniogmc at gmail dot com>
+ * Copyright (c) 2022, Antonio Gabriel Muñoz Conejo <antoniogmc at gmail dot com>
  * Distributed under the terms of the MIT License
  */
 package com.github.tonivade.vavr.effect;
diff --git a/lib/src/main/java/com/github/tonivade/vavr/effect/Unit.java b/lib/src/main/java/com/github/tonivade/vavr/effect/Unit.java
index 0f7c8c6..11b3583 100644
--- a/lib/src/main/java/com/github/tonivade/vavr/effect/Unit.java
+++ b/lib/src/main/java/com/github/tonivade/vavr/effect/Unit.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2021, Antonio Gabriel Muñoz Conejo <antoniogmc at gmail dot com>
+ * Copyright (c) 2022, Antonio Gabriel Muñoz Conejo <antoniogmc at gmail dot com>
  * Distributed under the terms of the MIT License
  */
 package com.github.tonivade.vavr.effect;
diff --git a/lib/src/test/java/com/github/tonivade/vavr/effect/IOTest.java b/lib/src/test/java/com/github/tonivade/vavr/effect/IOTest.java
index 94f0931..59d9477 100644
--- a/lib/src/test/java/com/github/tonivade/vavr/effect/IOTest.java
+++ b/lib/src/test/java/com/github/tonivade/vavr/effect/IOTest.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2021, Antonio Gabriel Muñoz Conejo <antoniogmc at gmail dot com>
+ * Copyright (c) 2022, Antonio Gabriel Muñoz Conejo <antoniogmc at gmail dot com>
  * Distributed under the terms of the MIT License
  */
 package com.github.tonivade.vavr.effect;
@@ -37,10 +37,10 @@
 import io.vavr.control.Try;
 
 @ExtendWith(MockitoExtension.class)
-public class IOTest {
+class IOTest {
 
   @Test
-  public void pure() {
+  void pure() {
     IO<String> pure = IO.pure("hola mundo");
 
     assertAll(
@@ -52,7 +52,7 @@
   }
   
   @Test
-  public void asyncSuccess() {
+  void asyncSuccess() {
     IO<String> async = IO.async(callback -> {
       System.out.println(Thread.currentThread().getName());
       Thread.sleep(100);
@@ -65,7 +65,7 @@
   }
   
   @Test
-  public void asyncFailure() {
+  void asyncFailure() {
     IO<String> async = IO.async(callback -> {
       Thread.sleep(100);
       callback.accept(Try.failure(new UnsupportedOperationException()));
@@ -77,7 +77,7 @@
   }
 
 //  @Test
-//  public void echo() {
+//  void echo() {
 //    IO<Unit> echo = narrowK(console.println("write your name"))
 //        .andThen(narrowK(console.readln()))
 //        .flatMap(name -> narrowK(console.println("Hello " + name)))
@@ -91,7 +91,7 @@
 //  }
 
   @Test
-  public void safeRunAsync() {
+  void safeRunAsync() {
     IO<List<String>> program = currentThreadIO();
 
     Try<List<String>> result = program.runAsync().await(1, TimeUnit.SECONDS).toTry();
@@ -100,7 +100,7 @@
   }
 
   @Test
-  public void bracket() throws SQLException {
+  void bracket() throws SQLException {
     ResultSet resultSet = mock(ResultSet.class);
     when(resultSet.getString("id")).thenReturn("value");
 
@@ -111,14 +111,14 @@
   }
 
   @Test
-  public void safeRunAsyncSuccess(@Mock Consumer<? super Try<? extends String>> callback) {
+  void safeRunAsyncSuccess(@Mock Consumer<? super Try<? extends String>> callback) {
     IO.pure("hola").safeRunAsync(callback);
 
     verify(callback, timeout(1000)).accept(Try.success("hola"));
   }
 
   @Test
-  public void unsafeRunAsyncFailure(@Mock Consumer<? super Try<? extends String>> callback) {
+  void unsafeRunAsyncFailure(@Mock Consumer<? super Try<? extends String>> callback) {
     RuntimeException error = new RuntimeException();
 
     IO.<String>raiseError(error).safeRunAsync(callback);
@@ -127,14 +127,14 @@
   }
 
   @Test
-  public void recover() {
+  void recover() {
     IO<String> recover = IO.<String>raiseError(new RuntimeException()).recover(error -> "hola mundo");
 
     assertEquals("hola mundo", recover.unsafeRunSync());
   }
 
   @Test
-  public void recoverWith() {
+  void recoverWith() {
     IO<String> recover = IO.<String>raiseError(new IllegalArgumentException())
         .recover(IllegalArgumentException.class, error -> "hola mundo");
 
@@ -142,7 +142,7 @@
   }
 
   @Test
-  public void recoverWithNotMatch() {
+  void recoverWithNotMatch() {
     IO<String> recover = IO.<String>raiseError(new IllegalArgumentException())
         .recover(NoSuchElementException.class, error -> "hola mundo");
 
@@ -150,7 +150,7 @@
   }
 
   @Test
-  public void retry(@Mock Supplier<String> computation) {
+  void retry(@Mock Supplier<String> computation) {
     when(computation.get()).thenThrow(UnsupportedOperationException.class);
 
     Try<String> retry = IO.task(computation).retry().safeRunSync();
@@ -160,7 +160,7 @@
   }
 
   @Test
-  public void retryFailure(@Mock Supplier<String> computation) {
+  void retryFailure(@Mock Supplier<String> computation) {
     when(computation.get()).thenThrow(UnsupportedOperationException.class);
 
     Try<String> retry = IO.task(computation).retry(Duration.ofMillis(100), 3).safeRunSync();
@@ -170,7 +170,7 @@
   }
 
   @Test
-  public void retrySuccess(@Mock Supplier<String> computation) {
+  void retrySuccess(@Mock Supplier<String> computation) {
     when(computation.get())
         .thenThrow(UnsupportedOperationException.class)
         .thenThrow(UnsupportedOperationException.class)
@@ -184,7 +184,7 @@
   }
 
   @Test
-  public void repeatSuccess(@Mock Supplier<String> computation) {
+  void repeatSuccess(@Mock Supplier<String> computation) {
     when(computation.get()).thenReturn("hola");
 
     Try<String> repeat = IO.task(computation).repeat(Duration.ofMillis(100), 3).safeRunSync();
@@ -194,7 +194,7 @@
   }
 
   @Test
-  public void repeatFailure(@Mock Supplier<String> computation) {
+  void repeatFailure(@Mock Supplier<String> computation) {
     when(computation.get()).thenReturn("hola").thenThrow(UnsupportedOperationException.class);
 
     Try<String> repeat = IO.task(computation).repeat(Duration.ofMillis(100), 3).safeRunSync();
@@ -204,7 +204,7 @@
   }
 
   @Test
-  public void repeat(@Mock Supplier<String> computation) {
+  void repeat(@Mock Supplier<String> computation) {
     when(computation.get()).thenReturn("hola");
 
     Try<String> repeat = IO.task(computation).repeat().safeRunSync();
@@ -214,7 +214,7 @@
   }
 
   @Test
-  public void flatMapped() {
+  void flatMapped() {
     IO<String> io = IO.unit()
         .map(ignore -> "hola")
         .map(ignore -> "hola")
@@ -225,7 +225,7 @@
   }
 
   @Test
-  public void stackSafety() {
+  void stackSafety() {
     IO<Integer> sum = sum(100000, 0);
 
     Future<Integer> futureSum = sum.runAsync();
@@ -235,7 +235,7 @@
   }
 
   @Test
-  public void timed() {
+  void timed() {
     IO<Tuple2<Duration, Integer>> sum = sum(100000, 0).timed();
 
     Tuple2<Duration, Integer> result = sum.unsafeRunSync();
@@ -245,17 +245,17 @@
   }
   
   @Test
-  public void timeoutFail() {
+  void timeoutFail() {
     assertThrows(TimeoutException.class, IO.never().timeout(Duration.ofSeconds(1))::unsafeRunSync);
   }
   
   @Test
-  public void timeoutSuccess() {
+  void timeoutSuccess() {
     assertEquals(1, IO.pure(1).timeout(Duration.ofSeconds(1)).unsafeRunSync());
   }
   
   @Test
-  public void traverse() {
+  void traverse() {
     IO<String> left = IO.task(() -> "left");
     IO<String> right = IO.task(() -> "right");
     
@@ -265,7 +265,7 @@
   }
 
   @Test
-  public void raceA() {
+  void raceA() {
     IO<Either<Integer, String>> race = IO.race(
         IO.delay(Duration.ofMillis(10), () -> 10),
         IO.delay(Duration.ofMillis(100), () -> "b"));
@@ -276,7 +276,7 @@
   }
 
   @Test
-  public void raceB() {
+  void raceB() {
     IO<Either<Integer, String>> race = IO.race(
         IO.delay(Duration.ofMillis(100), () -> 10),
         IO.delay(Duration.ofMillis(10), () -> "b"));
@@ -287,7 +287,7 @@
   }
   
   @Test
-  public void fork() {
+  void fork() {
     IO<String> result = IO.pure("hola")
       .flatMap(hello -> IO.delay(Duration.ofSeconds(1), () -> hello + " toni").fork())
       .flatMap(Fiber::join);
@@ -298,7 +298,7 @@
   }
   
   @Test
-  public void memoize(@Mock Function1<String, String> toUpperCase) {
+  void memoize(@Mock Function1<String, String> toUpperCase) {
     when(toUpperCase.apply(any()))
       .thenAnswer(args -> args.getArgument(0, String.class).toUpperCase());
     
@@ -314,7 +314,7 @@
   }
   
   @Test
-  public void fibSyncTest() {
+  void fibSyncTest() {
     assertAll(
         () -> assertEquals(1, fibSync(1).unsafeRunSync()),
         () -> assertEquals(1, fibSync(2).unsafeRunSync()),
@@ -330,7 +330,7 @@
   }
   
   @Test
-  public void fibAsyncTest() {
+  void fibAsyncTest() {
     assertAll(
         () -> assertEquals(1, fibAsync(1).unsafeRunSync()),
         () -> assertEquals(1, fibAsync(2).unsafeRunSync()),