squid:S1319 - Declarations should use Java collection interfaces such as List rather than specific implementation classes such as LinkedList

caching/src/main/java/com/iluwatar/caching/CacheStore.java

@@ -22,7 +22,7 @@
  */
 package com.iluwatar.caching;
 
-import java.util.ArrayList;
+import java.util.List;
 
 /**
  *
@@ -134,7 +134,7 @@ public class CacheStore {
     if (null == cache) {
       return;
     }
-    ArrayList<UserAccount> listOfUserAccounts = cache.getCacheDataInListForm();
+    List<UserAccount> listOfUserAccounts = cache.getCacheDataInListForm();
     for (UserAccount userAccount : listOfUserAccounts) {
       DbManager.upsertDb(userAccount);
     }
@@ -144,7 +144,7 @@ public class CacheStore {
    * Print user accounts
    */
   public static String print() {
-    ArrayList<UserAccount> listOfUserAccounts = cache.getCacheDataInListForm();
+    List<UserAccount> listOfUserAccounts = cache.getCacheDataInListForm();
     StringBuilder sb = new StringBuilder();
     sb.append("\n--CACHE CONTENT--\n");
     for (UserAccount userAccount : listOfUserAccounts) {

caching/src/main/java/com/iluwatar/caching/DbManager.java

@@ -24,6 +24,7 @@ package com.iluwatar.caching;
 
 import java.text.ParseException;
 import java.util.HashMap;
+import java.util.Map;
 
 import org.bson.Document;
 
@@ -49,7 +50,7 @@ public final class DbManager {
   private static MongoDatabase db;
   private static boolean useMongoDB;
 
-  private static HashMap<String, UserAccount> virtualDB;
+  private static Map<String, UserAccount> virtualDB;
 
   private DbManager() {
   }

caching/src/main/java/com/iluwatar/caching/LruCache.java

@@ -24,6 +24,8 @@ package com.iluwatar.caching;
 
 import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
 
 /**
  *
@@ -49,7 +51,7 @@ public class LruCache {
   }
 
   int capacity;
-  HashMap<String, Node> cache = new HashMap<>();
+  Map<String, Node> cache = new HashMap<>();
   Node head;
   Node end;
 
@@ -161,7 +163,7 @@ public class LruCache {
    *
    * Returns cache data in list form.
    */
-  public ArrayList<UserAccount> getCacheDataInListForm() {
+  public List<UserAccount> getCacheDataInListForm() {
     ArrayList<UserAccount> listOfCacheData = new ArrayList<>();
     Node temp = head;
     while (temp != null) {