added more example

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

@@ -0,0 +1,5 @@
+
+public class Building {
+	public void paint() {
+	}
+}

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

@@ -1,4 +1,5 @@
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 
 public class Generics {
@@ -6,19 +7,24 @@ public class Generics {
 	// definition of a generic method
 	public static <T> List<T> fromArrayToList(T[] a) {
 		List<T> list = new ArrayList<>();
-		for (T t : a) {
+		Arrays.stream(a).forEach(list::add);
-			list.add(t);
-		}
 		return list;
 	}
 
 	// example of a generic method that has Number as an upper bound for T
 	public static <T extends Number> List<T> fromArrayToListWithUpperBound(T[] a) {
 		List<T> list = new ArrayList<>();
-		for (T t : a) {
+		Arrays.stream(a).forEach(list::add);
-			list.add(t);
-		}
 		return list;
 	}
 
+	// 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) {
+		for (Building building : buildings) {
+			building.paint();
+		}
+		return true;
+	}
+
 }

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

@@ -0,0 +1,4 @@
+
+public class SubBuilding extends Building {
+
+}

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

@@ -1,4 +1,8 @@
-import java.util.Iterator;
+import static org.hamcrest.CoreMatchers.hasItems;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.junit.Assert.assertTrue;
+
+import java.util.ArrayList;
 import java.util.List;
 
 import org.junit.Test;
@@ -7,40 +11,45 @@ public class GenericsTest {
 
 	// testing the generic method with Integer
 	@Test
-	public void fromArrayToListIntTest() {
+	public void givenArrayOfIntegers_thanListOfIntegersReturnedOK() {
 		Integer[] intArray = { 1, 2, 3, 4, 5 };
 		List<Integer> list = Generics.fromArrayToList(intArray);
-		Iterator<Integer> iterator;
+
-		iterator = list.iterator();
+		assertThat(list, hasItems(intArray));
-		while (iterator.hasNext()) {
-			System.out.println(iterator.next());
-		}
 	}
 
 	// testing the generic method with String
 	@Test
-	public void fromArrayToListStringTest() {
+	public void givenArrayOfStrings_thanListOfStringsReturnedOK() {
 		String[] stringArray = { "hello1", "hello2", "hello3", "hello4", "hello5" };
 		List<String> list = Generics.fromArrayToList(stringArray);
-		Iterator<String> iterator;
+
-		iterator = list.iterator();
+		assertThat(list, hasItems(stringArray));
-		while (iterator.hasNext()) {
-			System.out.println(iterator.next());
-		}
 	}
 
 	// testing the generic method with Number as upper bound with Integer
 	// if we test fromArrayToListWithUpperBound with any type that doesn't
 	// extend Number it will fail to compile
 	@Test
-	public void fromArrayToListUpperboundIntTest() {
+	public void givenArrayOfIntegersAndNumberUpperBound_thanListOfIntegersReturnedOK() {
 		Integer[] intArray = { 1, 2, 3, 4, 5 };
 		List<Integer> list = Generics.fromArrayToListWithUpperBound(intArray);
-		Iterator<Integer> iterator;
+
-		iterator = list.iterator();
+		assertThat(list, hasItems(intArray));
-		while (iterator.hasNext()) {
-			System.out.println(iterator.next());
 	}
+
+	// testing paintAllBuildings method with a subtype of Building, the method
+	// will work with all subtypes of Building
+	@Test
+	public void givenSubTypeOfAwildCardBoundedGenericMethod() {
+
+		List<SubBuilding> subBuildingsList = new ArrayList<>();
+		subBuildingsList.add(new SubBuilding());
+		subBuildingsList.add(new SubBuilding());
+
+		boolean result = Generics.paintAllBuildings(subBuildingsList);
+		assertTrue(result);
+
 	}
 
 }