BAEL-5675 - variable initialization on declaration vs on constructor (#12800)

* BAEL-5675 - variable initialization on declaration vs on constructor

* moved classes under a different project

core-java-modules/core-java-lang-5/src/main/java/com/baeldung/variableInitialization/A.java

@@ -0,0 +1,13 @@
+package com.baeldung.variableInitialization;
+
+public class A {
+    private B b = new B();
+
+    public A() {
+        this.b = new B();
+    }
+
+    public A(B b) {
+        this.b = b;
+    }
+}

core-java-modules/core-java-lang-5/src/main/java/com/baeldung/variableInitialization/B.java

@@ -0,0 +1,4 @@
+package com.baeldung.variableInitialization;
+
+public class B {
+}

core-java-modules/core-java-lang-5/src/test/java/com/baeldung/variableinitialization/AUnitTest.java

@@ -0,0 +1,18 @@
+package com.baeldung.variableinitialization;
+
+import static org.mockito.Mockito.mock;
+
+import org.junit.jupiter.api.Test;
+
+import com.baeldung.variableInitialization.A;
+import com.baeldung.variableInitialization.B;
+
+public class AUnitTest {
+
+    @Test
+    public void whenCreatingTest_useDependencyInjection() {
+        // given
+        B b = mock(B.class);
+        A a = new A(b);
+    }
+}