Clear Sonar Blockers (#1643)

* remove debt from CachingTest

https://sonarcloud.io/project/issues?fileUuids=AW3G0SevwB6UiZzQNqXR&id=iluwatar_java-design-patterns&open=AXK0Ozo--CiGJS70dLl0&resolved=false
 
Signed-off-by: Subhrodip Mohanta <subhrodipmohanta@gmail.com>

* fixed few debts for Spatial Partition module

Mainly convertig Hashtable to HashMaps

Signed-off-by: Subhrodip Mohanta <subhrodipmohanta@gmail.com>

* fixed some logger norms

Signed-off-by: Subhrodip Mohanta <subhrodipmohanta@gmail.com>

* fixed few errors as it got mixed with the stash

Signed-off-by: Subhrodip Mohanta <subhrodipmohanta@gmail.com>

caching/src/test/java/com/iluwatar/caching/CachingTest.java

@@ -23,13 +23,15 @@
 
 package com.iluwatar.caching;
 
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
 /**
  * Application test
  */
-public class CachingTest {
+class CachingTest {
   private App app;
 
   /**
@@ -47,22 +49,26 @@ public class CachingTest {
   }
 
   @Test
-  public void testReadAndWriteThroughStrategy() {
+  void testReadAndWriteThroughStrategy() {
+	assertNotNull(app);
     app.useReadAndWriteThroughStrategy();
   }
 
   @Test
-  public void testReadThroughAndWriteAroundStrategy() {
+  void testReadThroughAndWriteAroundStrategy() {
+	assertNotNull(app);
     app.useReadThroughAndWriteAroundStrategy();
   }
 
   @Test
-  public void testReadThroughAndWriteBehindStrategy() {
+  void testReadThroughAndWriteBehindStrategy() {
+	assertNotNull(app);
     app.useReadThroughAndWriteBehindStrategy();
   }
 
   @Test
-  public void testCacheAsideStrategy() {
+  void testCacheAsideStrategy() {
+	assertNotNull(app);
     app.useCacheAsideStategy();
   }
 }