added generics example method and tests

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

@@ -0,0 +1,24 @@
+import java.util.ArrayList;
+import java.util.List;
+
+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) {
+			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) {
+			list.add(t);
+		}
+		return list;
+	}
+
+}

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

@@ -0,0 +1,46 @@
+import java.util.Iterator;
+import java.util.List;
+
+import org.junit.Test;
+
+public class GenericsTest {
+
+	// testing the generic method with Integer
+	@Test
+	public void fromArrayToListIntTest() {
+		Integer[] intArray = { 1, 2, 3, 4, 5 };
+		List<Integer> list = Generics.fromArrayToList(intArray);
+		Iterator<Integer> iterator;
+		iterator = list.iterator();
+		while (iterator.hasNext()) {
+			System.out.println(iterator.next());
+		}
+	}
+
+	// testing the generic method with String
+	@Test
+	public void fromArrayToListStringTest() {
+		String[] stringArray = { "hello1", "hello2", "hello3", "hello4", "hello5" };
+		List<String> list = Generics.fromArrayToList(stringArray);
+		Iterator<String> iterator;
+		iterator = list.iterator();
+		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() {
+		Integer[] intArray = { 1, 2, 3, 4, 5 };
+		List<Integer> list = Generics.fromArrayToListWithUpperBound(intArray);
+		Iterator<Integer> iterator;
+		iterator = list.iterator();
+		while (iterator.hasNext()) {
+			System.out.println(iterator.next());
+		}
+	}
+
+}