BAEL-376 - changing method signatures

core-java/src/main/java/com/baeldung/generics/Building.java

@@ -7,6 +7,6 @@ public class Building {
 	private static final Logger LOGGER = LoggerFactory.getLogger(Building.class);
 
 	public void paint() {
-		LOGGER.info("Building");
+		LOGGER.info("Painting Building");
 	}
 }

core-java/src/main/java/com/baeldung/generics/Generics.java

@@ -1,27 +1,34 @@
 package com.baeldung.generics;
 
-import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.function.Function;
 import java.util.stream.Collectors;
 
 public class Generics {
 
-	// definition of a generic method
-	public static <T> List<T> fromArrayToList(T[] a) {
-		return Arrays.stream(a).collect(Collectors.toList());
-	}
+    // definition of a generic method
+    public static <T> List<T> fromArrayToList(T[] a) {
+        return Arrays.stream(a).collect(Collectors.toList());
+    }
 
-	// example of a generic method that has Number as an upper bound for T
-	public static <T extends Number> List<T> fromArrayToListWithUpperBound(T[] a) {
-		return Arrays.stream(a).collect(Collectors.toList());
-	}
+    // definition of a generic method
+    public static <T, G> List<G> fromArrayToList(T[] a, List<G> list, Function<T, G> mapperFunction) {
+        List<T> listWithTypeT = Arrays.stream(a).collect(Collectors.toList());
+        return listWithTypeT.stream().map(mapperFunction)
+          .collect(Collectors.toList());
+    }
 
-	// example of a generic method with a wild card, this method can be used
-	// with a list of any subtype of Building
-	public static boolean paintAllBuildings(List<? extends Building> buildings) {
-		buildings.forEach(Building::paint);
-		return true;
-	}
+
+    // example of a generic method that has Number as an upper bound for T
+    public static <T extends Number> List<T> fromArrayToListWithUpperBound(T[] a) {
+        return Arrays.stream(a).collect(Collectors.toList());
+    }
+
+    // example of a generic method with a wild card, this method can be used
+    // with a list of any subtype of Building
+    public static void paintAllBuildings(List<? extends Building> buildings) {
+        buildings.forEach(Building::paint);
+    }
 
 }

core-java/src/main/java/com/baeldung/generics/House.java

@@ -7,6 +7,6 @@ public class House extends Building {
     private static final Logger LOGGER = LoggerFactory.getLogger(House.class);
 
     public void paint() {
-        LOGGER.info("House");
+        LOGGER.info("Painting House");
     }
 }

core-java/src/test/java/com/baeldung/generics/GenericsTest.java

@@ -7,7 +7,7 @@ import java.util.List;
 
 import static org.hamcrest.CoreMatchers.hasItems;
 import static org.hamcrest.MatcherAssert.assertThat;
-import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
 
 public class GenericsTest {
 
@@ -20,6 +20,15 @@ public class GenericsTest {
         assertThat(list, hasItems(intArray));
     }
 
+    // testing the generic method with Integer and String type
+    @Test
+    public void givenArrayOfIntegers_thanListOfStringReturnedOK() {
+        Integer[] intArray = {1, 2, 3, 4, 5};
+        List<String> stringList = new ArrayList<>();
+        stringList = Generics.fromArrayToList(intArray, stringList, Object::toString);
+        assertThat(stringList, hasItems("1", "2", "3", "4", "5"));
+    }
+
     // testing the generic method with String
     @Test
     public void givenArrayOfStrings_thanListOfStringsReturnedOK() {
@@ -43,14 +52,19 @@ public class GenericsTest {
     // testing paintAllBuildings method with a subtype of Building, the method
     // will work with all subtypes of Building
     @Test
-    public void givenSubTypeOfWildCardBoundedGenericMethod_thanOK() {
+    public void givenSubTypeOfWildCardBoundedGenericType_thanPaintingOK() {
+        try {
+            List<Building> subBuildingsList = new ArrayList<>();
+            subBuildingsList.add(new Building());
+            subBuildingsList.add(new House());
 
-        List<Building> subBuildingsList = new ArrayList<>();
-        subBuildingsList.add(new Building());
-        subBuildingsList.add(new House());
-
-        boolean result = Generics.paintAllBuildings(subBuildingsList);
-        assertTrue(result);
+            // prints
+            // Painting Building
+            // Painting House
+            Generics.paintAllBuildings(subBuildingsList);
+        } catch (Exception e) {
+            fail();
+        }
     }
 
 }