Added a new Class and few test cases to the core-java-modules (#11867)

* added a new project: hexagonal architecture

* Added some test cases for the project

* Added a new project to demo the error: variable might not have been initialized

* Added a new Class to the core-java-modules

* Added a New Class to the core-java-module

core-java-modules/core-java-exceptions-4/src/main/java/com/baeldung/exception/variablemightnothavebeeninitialized/VariableMightNotHaveBeenInitialized.java

@@ -0,0 +1,45 @@
+package com.baeldung.exception.variablemightnothavebeeninitialized;
+
+public class VariableMightNotHaveBeenInitialized {
+
+    private static int instanceVariableCount;
+
+    /**
+     * Method would not compile if lines 14 and 18 are uncommented.
+     */
+    public static void countEven() {
+        //uninstantiated
+        int count;
+        int[] arr = new int[]{23, 56, 89, 12, 23};
+        for (int i = 0; i < arr.length; i++) {
+            if ((arr[i] % 2) == 0) {
+                // count++;
+            }
+
+        }
+        // System.out.println("Total Even Numbers : " + count);
+    }
+
+    public static int countEvenUsingInstanceVariable(int[] arr) {
+
+        for (int i = 0; i < arr.length; i++) {
+            if ((arr[i] % 2) == 0) {
+                instanceVariableCount++;
+            }
+
+        }
+        return instanceVariableCount;
+    }
+
+    public static int countEvenUsingIfElse(int[] arr, int args) {
+        int count;
+        count = args > 0 ? args : 0;
+        for (int i = 0; i < arr.length; i++) {
+            if ((arr[i] % 2) == 0) {
+                count++;
+            }
+
+        }
+        return count;
+    }
+}

core-java-modules/core-java-exceptions-4/src/test/java/com/baeldung/exception/variablemightnothavebeeninitialized/VariableMightNotHaveBeenInitializedUnitTest.java

@@ -0,0 +1,24 @@
+package com.baeldung.exception.variablemightnothavebeeninitialized;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class VariableMightNotHaveBeenInitializedUnitTest {
+
+    @Test
+    public void usingInstanceVariable_returnCount() {
+        int[] arr = new int[]{1, 2, 3, 4, 5, 6};
+        int value = VariableMightNotHaveBeenInitialized.countEvenUsingInstanceVariable(arr);
+
+        assertEquals(3, value);
+    }
+
+    @Test
+    public void usingArgumentsAndIfElse_returnCount() {
+        int[] arr = new int[]{1, 2, 3, 4, 5, 6};
+        int value = VariableMightNotHaveBeenInitialized.countEvenUsingIfElse(arr, 2);
+
+        assertEquals(5, value);
+    }
+}