Future in Vavr

vavr/src/main/java/com/baeldung/vavr/future/Util.java

@@ -9,4 +9,12 @@ public class Util {
     public static int divideByZero(int num) {
         return num / 0;
     }
+
+    public static String getSubstringMinusOne(String s) {
+        return s.substring(-1);
+    }
+
+    public static String getSubstringMinusTwo(String s) {
+        return s.substring(-2);
+    }
 }

vavr/src/test/java/com/baeldung/vavr/future/FutureTest.java

@@ -4,6 +4,7 @@ import static org.assertj.core.api.Assertions.assertThat;
 
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ExecutionException;
+import java.util.concurrent.Executors;
 
 import org.junit.Test;
 
@@ -15,6 +16,17 @@ import io.vavr.control.Try;
 
 public class FutureTest {
 
+    @Test
+    public void whenChangeExecutorService_thenCorrect() {
+        String initialValue = "Welcome to ";
+        Future<String> resultFuture = Future.of(
+          Executors.newSingleThreadExecutor(),
+          () -> Util.appendData(initialValue));
+        String result = resultFuture.get();
+
+        assertThat(result).isEqualTo("Welcome to Baeldung!");
+    }
+
     @Test
     public void whenAppendData_thenCorrect1() {
         String initialValue = "Welcome to ";
@@ -40,8 +52,8 @@ public class FutureTest {
     public void whenAppendData_thenSuccess() {
         String initialValue = "Welcome to ";
         Future<String> resultFuture = Future.of(() -> Util.appendData(initialValue))
-            .onSuccess(finalResult -> System.out.println("Successfully Completed - Result: " + finalResult))
+          .onSuccess(finalResult -> System.out.println("Successfully Completed - Result: " + finalResult))
-            .onFailure(finalResult -> System.out.println("Failed - Result: " + finalResult));
+          .onFailure(finalResult -> System.out.println("Failed - Result: " + finalResult));
         String result = resultFuture.get();
 
         assertThat(result).isEqualTo("Welcome to Baeldung!");
@@ -51,8 +63,8 @@ public class FutureTest {
     public void whenChainingCallbacks_thenCorrect() {
         String initialValue = "Welcome to ";
         Future<String> resultFuture = Future.of(() -> Util.appendData(initialValue))
-            .andThen(finalResult -> System.out.println("Completed - 1: " + finalResult))
+          .andThen(finalResult -> System.out.println("Completed - 1: " + finalResult))
-            .andThen(finalResult -> System.out.println("Completed - 2: " + finalResult));
+          .andThen(finalResult -> System.out.println("Completed - 2: " + finalResult));
         String result = resultFuture.get();
 
         assertThat(result).isEqualTo("Welcome to Baeldung!");
@@ -109,14 +121,14 @@ public class FutureTest {
     @Test
     public void whenCallZip_thenCorrect() {
         Future<Tuple2<String, Integer>> future = Future.of(() -> "John")
-            .zip(Future.of(() -> new Integer(5)));
+          .zip(Future.of(() -> new Integer(5)));
         future.await();
 
         assertThat(future.get()).isEqualTo(Tuple.of("John", new Integer(5)));
     }
 
     @Test
-    public void whenAppendData_thenFutureNotEmptyd() throws InterruptedException, ExecutionException {
+    public void whenConvertToCompletableFuture_thenCorrect() throws InterruptedException, ExecutionException {
         String initialValue = "Welcome to ";
         Future<String> resultFuture = Future.of(() -> Util.appendData(initialValue));
         CompletableFuture<String> convertedFuture = resultFuture.toCompletableFuture();
@@ -127,9 +139,39 @@ public class FutureTest {
     @Test
     public void whenCallMap_thenCorrect() {
         Future<String> futureResult = Future.of(() -> new StringBuilder("from Baeldung"))
-            .map(a -> "Hello " + a);
+          .map(a -> "Hello " + a);
         futureResult.await();
 
         assertThat(futureResult.get()).isEqualTo("Hello from Baeldung");
     }
+
+    @Test
+    public void whenFutureFails_thenGetErrorMessage() {
+        Future<String> resultFuture = Future.of(() -> Util.getSubstringMinusOne("Hello"));
+        Future<String> errorMessageFuture = resultFuture.recover(Throwable::getMessage);
+        String errorMessage = errorMessageFuture.get();
+
+        assertThat(errorMessage).isEqualTo("String index out of range: -1");
+    }
+
+    @Test
+    public void whenFutureFails_thenGetAnotherFuture() {
+        Future<String> resultFuture = Future.of(() -> Util.getSubstringMinusOne("Hello"));
+        Future<String> errorMessageFuture = resultFuture.recoverWith(a -> Future.of(a::getMessage));
+        String errorMessage = errorMessageFuture.get();
+
+        assertThat(errorMessage).isEqualTo("String index out of range: -1");
+    }
+
+    @Test
+    public void whenBothFuturesFail_thenGetErrorMessage() {
+        Future<String> future1 = Future.of(() -> Util.getSubstringMinusOne("Hello"));
+        Future<String> future2 = Future.of(() -> Util.getSubstringMinusTwo("Hello"));
+        Future<String> errorMessageFuture = future1.fallbackTo(future2);
+        Future<Throwable> errorMessage = errorMessageFuture.failed();
+        
+        assertThat(
+          errorMessage.get().getMessage())
+          .isEqualTo("String index out of range: -1");
+    }
 }