Java 11 migration: patterns starting with a (iluwatar#1084)

* Moves abstract-factory pattern to java 11

* Moves abstract-document pattern to java 11

* Moves acyclic-visitor pattern to java 11

* Moves adapter pattern to java 11

* Moves aggregator-microservices pattern to java 11

* Moves api-gateway pattern to java 11

Author: anuragagarwal561994

abstract-document/src/main/java/com/iluwatar/abstractdocument/AbstractDocument.java

@@ -23,10 +23,10 @@
 
 package com.iluwatar.abstractdocument;
 
+import java.util.Collection;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
-import java.util.Optional;
 import java.util.function.Function;
 import java.util.stream.Stream;
 
@@ -55,9 +55,13 @@ public Object get(String key) {
 
   @Override
   public <T> Stream<T> children(String key, Function<Map<String, Object>, T> constructor) {
-    Optional<List<Map<String, Object>>> any = Stream.of(get(key)).filter(Objects::nonNull)
-        .map(el -> (List<Map<String, Object>>) el).findAny();
-    return any.map(maps -> maps.stream().map(constructor)).orElseGet(Stream::empty);
+    return Stream.ofNullable(get(key))
+        .filter(Objects::nonNull)
+        .map(el -> (List<Map<String, Object>>) el)
+        .findAny()
+        .stream()
+        .flatMap(Collection::stream)
+        .map(constructor);
   }
 
   @Override

abstract-document/src/main/java/com/iluwatar/abstractdocument/App.java

@@ -66,11 +66,14 @@ public App() {
     var car = new Car(carProperties);
 
     LOGGER.info("Here is our car:");
-    LOGGER.info("-> model: {}", car.getModel().get());
-    LOGGER.info("-> price: {}", car.getPrice().get());
+    LOGGER.info("-> model: {}", car.getModel().orElseThrow());
+    LOGGER.info("-> price: {}", car.getPrice().orElseThrow());
     LOGGER.info("-> parts: ");
-    car.getParts().forEach(p -> LOGGER
-        .info("\t{}/{}/{}", p.getType().get(), p.getModel().get(), p.getPrice().get()));
+    car.getParts().forEach(p -> LOGGER.info("\t{}/{}/{}",
+        p.getType().orElse(null),
+        p.getModel().orElse(null),
+        p.getPrice().orElse(null))
+    );
   }
 
   /**

abstract-document/src/test/java/com/iluwatar/abstractdocument/AbstractDocumentTest.java

@@ -23,14 +23,14 @@
 
 package com.iluwatar.abstractdocument;
 
-import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.stream.Stream;
-
-import static org.junit.jupiter.api.Assertions.*;
+import org.junit.jupiter.api.Test;
 
 /**
  * AbstractDocument test class
@@ -61,22 +61,22 @@ public void shouldRetrieveChildren() {
 
     document.put(KEY, children);
 
-    Stream<DocumentImplementation> childrenStream = document.children(KEY, DocumentImplementation::new);
+    var childrenStream = document.children(KEY, DocumentImplementation::new);
     assertNotNull(children);
     assertEquals(2, childrenStream.count());
   }
 
   @Test
   public void shouldRetrieveEmptyStreamForNonExistingChildren() {
-    Stream<DocumentImplementation> children = document.children(KEY, DocumentImplementation::new);
+    var children = document.children(KEY, DocumentImplementation::new);
     assertNotNull(children);
     assertEquals(0, children.count());
   }
 
   @Test
   public void shouldIncludePropsInToString() {
-    Map<String, Object> props = Map.of(KEY, VALUE);
-    DocumentImplementation document = new DocumentImplementation(props);
+    var props = Map.of(KEY, (Object) VALUE);
+    var document = new DocumentImplementation(props);
     assertTrue(document.toString().contains(KEY));
     assertTrue(document.toString().contains(VALUE));
   }

abstract-document/src/test/java/com/iluwatar/abstractdocument/DomainTest.java

@@ -23,15 +23,14 @@
 
 package com.iluwatar.abstractdocument;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
 import com.iluwatar.abstractdocument.domain.Car;
 import com.iluwatar.abstractdocument.domain.Part;
 import com.iluwatar.abstractdocument.domain.enums.Property;
-import org.junit.jupiter.api.Test;
-
 import java.util.List;
 import java.util.Map;
-
-import static org.junit.jupiter.api.Assertions.assertEquals;
+import org.junit.jupiter.api.Test;
 
 /**
  * Test for Part and Car
@@ -47,27 +46,27 @@ public class DomainTest {
 
   @Test
   public void shouldConstructPart() {
-    Map<String, Object> partProperties = Map.of(
-            Property.TYPE.toString(), TEST_PART_TYPE,
-            Property.MODEL.toString(), TEST_PART_MODEL,
-            Property.PRICE.toString(), TEST_PART_PRICE);
-    Part part = new Part(partProperties);
-
-    assertEquals(TEST_PART_TYPE, part.getType().get());
-    assertEquals(TEST_PART_MODEL, part.getModel().get());
-    assertEquals(TEST_PART_PRICE, part.getPrice().get());
+    var partProperties = Map.of(
+        Property.TYPE.toString(), TEST_PART_TYPE,
+        Property.MODEL.toString(), TEST_PART_MODEL,
+        Property.PRICE.toString(), (Object) TEST_PART_PRICE
+    );
+    var part = new Part(partProperties);
+    assertEquals(TEST_PART_TYPE, part.getType().orElseThrow());
+    assertEquals(TEST_PART_MODEL, part.getModel().orElseThrow());
+    assertEquals(TEST_PART_PRICE, part.getPrice().orElseThrow());
   }
 
   @Test
   public void shouldConstructCar() {
-    Map<String, Object> carProperties = Map.of(
-            Property.MODEL.toString(), TEST_CAR_MODEL,
-            Property.PRICE.toString(), TEST_CAR_PRICE,
-            Property.PARTS.toString(), List.of(Map.of(), Map.of()));
-    Car car = new Car(carProperties);
-
-    assertEquals(TEST_CAR_MODEL, car.getModel().get());
-    assertEquals(TEST_CAR_PRICE, car.getPrice().get());
+    var carProperties = Map.of(
+        Property.MODEL.toString(), TEST_CAR_MODEL,
+        Property.PRICE.toString(), TEST_CAR_PRICE,
+        Property.PARTS.toString(), List.of(Map.of(), Map.of())
+    );
+    var car = new Car(carProperties);
+    assertEquals(TEST_CAR_MODEL, car.getModel().orElseThrow());
+    assertEquals(TEST_CAR_PRICE, car.getPrice().orElseThrow());
     assertEquals(2, car.getParts().count());
   }
 

abstract-factory/README.md

@@ -109,10 +109,10 @@ public class OrcKingdomFactory implements KingdomFactory {
 Now we have our abstract factory that lets us make family of related objects i.e. Elven kingdom factory creates Elven castle, king and army etc.
 
 ```java
-KingdomFactory factory = new ElfKingdomFactory();
-Castle castle = factory.createCastle();
-King king = factory.createKing();
-Army army = factory.createArmy();
+var factory = new ElfKingdomFactory();
+var castle = factory.createCastle();
+var king = factory.createKing();
+var army = factory.createArmy();
 
 castle.getDescription();  // Output: This is the Elven castle!
 king.getDescription(); // Output: This is the Elven king!
@@ -143,7 +143,7 @@ public static class FactoryMaker {
 }
 
 public static void main(String[] args) {
-  App app = new App();
+  var app = new App();
 
   LOGGER.info("Elf Kingdom");
   app.createKingdom(FactoryMaker.makeFactory(KingdomType.ELF));

abstract-factory/src/main/java/com/iluwatar/abstractfactory/App.java

@@ -128,7 +128,7 @@ public static KingdomFactory makeFactory(KingdomType type) {
    */
   public static void main(String[] args) {
 
-    App app = new App();
+    var app = new App();
 
     LOGGER.info("Elf Kingdom");
     app.createKingdom(FactoryMaker.makeFactory(KingdomType.ELF));

abstract-factory/src/test/java/com/iluwatar/abstractfactory/AbstractFactoryTest.java

@@ -28,7 +28,6 @@
 
 import com.iluwatar.abstractfactory.App.FactoryMaker;
 import com.iluwatar.abstractfactory.App.FactoryMaker.KingdomType;
-
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
@@ -49,40 +48,40 @@ public void setUp() {
 
   @Test
   public void king() {
-    final King elfKing = app.getKing(elfFactory);
+    final var elfKing = app.getKing(elfFactory);
     assertTrue(elfKing instanceof ElfKing);
     assertEquals(ElfKing.DESCRIPTION, elfKing.getDescription());
-    final King orcKing = app.getKing(orcFactory);
+    final var orcKing = app.getKing(orcFactory);
     assertTrue(orcKing instanceof OrcKing);
     assertEquals(OrcKing.DESCRIPTION, orcKing.getDescription());
   }
 
   @Test
   public void castle() {
-    final Castle elfCastle = app.getCastle(elfFactory);
+    final var elfCastle = app.getCastle(elfFactory);
     assertTrue(elfCastle instanceof ElfCastle);
     assertEquals(ElfCastle.DESCRIPTION, elfCastle.getDescription());
-    final Castle orcCastle = app.getCastle(orcFactory);
+    final var orcCastle = app.getCastle(orcFactory);
     assertTrue(orcCastle instanceof OrcCastle);
     assertEquals(OrcCastle.DESCRIPTION, orcCastle.getDescription());
   }
 
   @Test
   public void army() {
-    final Army elfArmy = app.getArmy(elfFactory);
+    final var elfArmy = app.getArmy(elfFactory);
     assertTrue(elfArmy instanceof ElfArmy);
     assertEquals(ElfArmy.DESCRIPTION, elfArmy.getDescription());
-    final Army orcArmy = app.getArmy(orcFactory);
+    final var orcArmy = app.getArmy(orcFactory);
     assertTrue(orcArmy instanceof OrcArmy);
     assertEquals(OrcArmy.DESCRIPTION, orcArmy.getDescription());
   }
 
   @Test
   public void createElfKingdom() {
     app.createKingdom(elfFactory);
-    final King king = app.getKing();
-    final Castle castle = app.getCastle();
-    final Army army = app.getArmy();
+    final var king = app.getKing();
+    final var castle = app.getCastle();
+    final var army = app.getArmy();
     assertTrue(king instanceof ElfKing);
     assertEquals(ElfKing.DESCRIPTION, king.getDescription());
     assertTrue(castle instanceof ElfCastle);
@@ -94,9 +93,9 @@ public void createElfKingdom() {
   @Test
   public void createOrcKingdom() {
     app.createKingdom(orcFactory);
-    final King king = app.getKing();
-    final Castle castle = app.getCastle();
-    final Army army = app.getArmy();
+    final var king = app.getKing();
+    final var castle = app.getCastle();
+    final var army = app.getArmy();
     assertTrue(king instanceof OrcKing);
     assertEquals(OrcKing.DESCRIPTION, king.getDescription());
     assertTrue(castle instanceof OrcCastle);

abstract-factory/src/test/java/com/iluwatar/abstractfactory/AppTest.java

@@ -25,15 +25,12 @@
 
 import org.junit.jupiter.api.Test;
 
-import java.io.IOException;
-
 /**
  * Tests that Abstract Factory example runs without errors.
  */
 public class AppTest {
   @Test
-  public void test() throws IOException {
-    String[] args = {};
-    App.main(args);
+  public void test() {
+    App.main(new String[]{});
   }
 }

acyclic-visitor/src/test/java/com/iluwatar/acyclicvisitor/AppTest.java

@@ -25,16 +25,13 @@
 
 import org.junit.jupiter.api.Test;
 
-import com.iluwatar.acyclicvisitor.App;
-
 /**
  * Tests that the Acyclic Visitor example runs without errors.
  */
 public class AppTest {
-  
+
   @Test
   public void test() {
-    String[] args = {};
-    App.main(args);  
+    App.main(new String[]{});
   }
 }

acyclic-visitor/src/test/java/com/iluwatar/acyclicvisitor/ConfigureForDosVisitorTest.java

@@ -37,7 +37,7 @@
  */
 public class ConfigureForDosVisitorTest {
 
-  TestLogger logger = TestLoggerFactory.getTestLogger(ConfigureForDosVisitor.class);
+  private TestLogger logger = TestLoggerFactory.getTestLogger(ConfigureForDosVisitor.class);
 
   @Test
   public void testVisitForZoom() {    
@@ -46,19 +46,21 @@ public void testVisitForZoom() {
 
     conDos.visit(zoom);
 
-    assertThat(logger.getLoggingEvents()).extracting("level", "message").contains(
-        tuple(INFO, zoom + " used with Dos configurator."));
+    assertThat(logger.getLoggingEvents())
+        .extracting("level", "message")
+        .contains(tuple(INFO, zoom + " used with Dos configurator."));
   }
 
   @Test
   public void testVisitForHayes() {
-    ConfigureForDosVisitor conDos = new ConfigureForDosVisitor();
-    Hayes hayes = new Hayes();
+    var conDos = new ConfigureForDosVisitor();
+    var hayes = new Hayes();
 
     conDos.visit(hayes);
 
-    assertThat(logger.getLoggingEvents()).extracting("level", "message").contains(
-        tuple(INFO, hayes + " used with Dos configurator."));
+    assertThat(logger.getLoggingEvents())
+        .extracting("level", "message")
+        .contains(tuple(INFO, hayes + " used with Dos configurator."));
   }
 
   @AfterEach

acyclic-visitor/src/test/java/com/iluwatar/acyclicvisitor/ConfigureForUnixVisitorTest.java

@@ -52,7 +52,8 @@ public void testVisitForZoom() {
 
     conUnix.visit(zoom);
 
-    assertThat(LOGGER.getLoggingEvents()).extracting("level", "message").contains(
-        tuple(INFO, zoom + " used with Unix configurator."));
+    assertThat(LOGGER.getLoggingEvents())
+        .extracting("level", "message")
+        .contains(tuple(INFO, zoom + " used with Unix configurator."));
   }
 }

adapter/README.md

@@ -93,7 +93,7 @@ public class FishingBoatAdapter implements RowingBoat {
 And now the `Captain` can use the `FishingBoat` to escape the pirates.
 
 ```java
-Captain captain = new Captain(new FishingBoatAdapter());
+var captain = new Captain(new FishingBoatAdapter());
 captain.row();
 ```