Fix 40 errors from checkstyle plugin run. 139 left))

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

@@ -1,26 +1,3 @@
-/*
- * The MIT License
- * Copyright © 2014-2021 Ilkka Seppälä
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
 package com.iluwatar.caching;
 
 import com.iluwatar.caching.database.DbManager;
@@ -28,33 +5,42 @@ import com.iluwatar.caching.database.DbManagerFactory;
 import lombok.extern.slf4j.Slf4j;
 
 /**
- * The Caching pattern describes how to avoid expensive re-acquisition of resources by not releasing
+ * The Caching pattern describes how to avoid expensive re-acquisition of
- * the resources immediately after their use. The resources retain their identity, are kept in some
+ * resources by not releasing the resources immediately after their use.
- * fast-access storage, and are re-used to avoid having to acquire them again. There are four main
+ * The resources retain their identity, are kept in some fast-access storage,
- * caching strategies/techniques in this pattern; each with their own pros and cons. They are;
+ * and are re-used to avoid having to acquire them again. There are four main
- * <code>write-through</code> which writes data to the cache and DB in a single transaction,
+ * caching strategies/techniques in this pattern; each with their own pros and
- * <code>write-around</code> which writes data immediately into the DB instead of the cache,
+ * cons. They are <code>write-through</code> which writes data to the cache and
- * <code>write-behind</code> which writes data into the cache initially whilst the data is only
+ * DB in a single transaction, <code>write-around</code> which writes data
- * written into the DB when the cache is full, and <code>cache-aside</code> which pushes the
+ * immediately into the DB instead of the cache, <code>write-behind</code>
- * responsibility of keeping the data synchronized in both data sources to the application itself.
+ * which writes data into the cache initially whilst the data is only
- * The <code>read-through</code> strategy is also included in the mentioned four strategies --
+ * written into the DB when the cache is full, and <code>cache-aside</code>
- * returns data from the cache to the caller <b>if</b> it exists <b>else</b> queries from DB and
+ * which pushes the responsibility of keeping the data synchronized in both
- * stores it into the cache for future use. These strategies determine when the data in the cache
+ * data sources to the application itself. The <code>read-through</code>
- * should be written back to the backing store (i.e. Database) and help keep both data sources
+ * strategy is also included in the mentioned four strategies --
- * synchronized/up-to-date. This pattern can improve performance and also helps to maintain
+ * returns data from the cache to the caller <b>if</b> it exists <b>else</b>
- * consistency between data held in the cache and the data in the underlying data store.
+ * queries from DB and stores it into the cache for future use. These strategies
+ * determine when the data in the cache should be written back to the backing
+ * store (i.e. Database) and help keep both data sources
+ * synchronized/up-to-date. This pattern can improve performance and also helps
+ * to maintainconsistency between data held in the cache and the data in
+ * the underlying data store.
  *
- * <p>In this example, the user account ({@link UserAccount}) entity is used as the underlying
+ * <p>In this example, the user account ({@link UserAccount}) entity is used
- * application data. The cache itself is implemented as an internal (Java) data structure. It adopts
+ * as the underlying application data. The cache itself is implemented as an
- * a Least-Recently-Used (LRU) strategy for evicting data from itself when its full. The four
+ * internal (Java) data structure. It adopts a Least-Recently-Used (LRU)
- * strategies are individually tested. The testing of the cache is restricted towards saving and
+ * strategy for evicting data from itself when its full. The four
- * querying of user accounts from the underlying data store ( {@link DbManager}). The main class (
+ * strategies are individually tested. The testing of the cache is restricted
- * {@link App} is not aware of the underlying mechanics of the application (i.e. save and query) and
+ * towards saving and querying of user accounts from the
- * whether the data is coming from the cache or the DB (i.e. separation of concern). The AppManager
+ * underlying data store( {@link DbManager}). The main class ( {@link App}
- * ({@link AppManager}) handles the transaction of data to-and-from the underlying data store
+ * is not aware of the underlying mechanics of the application
- * (depending on the preferred caching policy/strategy).
+ * (i.e. save and query) and whether the data is coming from the cache or the
+ * DB (i.e. separation of concern). The AppManager ({@link AppManager}) handles
+ * the transaction of data to-and-from the underlying data store (depending on
+ * the preferred caching policy/strategy).
  * <p>
- * <i>{@literal App --> AppManager --> CacheStore/LRUCache/CachingPolicy --> DBManager} </i>
+ * <i>{@literal App --> AppManager --> CacheStore/LRUCache/CachingPolicy -->
+ *     DBManager} </i>
  * </p>
  *
  * <p>
@@ -68,10 +54,20 @@ import lombok.extern.slf4j.Slf4j;
  */
 @Slf4j
 public class App {
+    /**
+     * Constant parameter name to use mongoDB.
+     */
     private static final String USE_MONGO_DB = "--mongo";
-    private AppManager appManager;
+    /**
+     * Application manager.
+     */
+    private final AppManager appManager;
 
-    public App(boolean isMongo) {
+    /**
+     * Constructor of current App.
+     * @param isMongo boolean
+     */
+    public App(final boolean isMongo) {
         DbManager dbManager = DbManagerFactory.initDb(isMongo);
         appManager = new AppManager(dbManager);
         appManager.initDb();
@@ -82,20 +78,20 @@ public class App {
      *
      * @param args command line args
      */
-    public static void main(String[] args) {
+    public static void main(final String[] args) {
         // VirtualDB (instead of MongoDB) was used in running the JUnit tests
         // and the App class to avoid Maven compilation errors. Set flag to
         // true to run the tests with MongoDB (provided that MongoDB is
         // installed and socket connection is open).
         App app = new App(isDbMongo(args));
         app.useReadAndWriteThroughStrategy();
-        System.out.println("=====================================================");
+        System.out.println("==============================================");
         app.useReadThroughAndWriteAroundStrategy();
-        System.out.println("=====================================================");
+        System.out.println("==============================================");
         app.useReadThroughAndWriteBehindStrategy();
-        System.out.println("=====================================================");
+        System.out.println("==============================================");
         app.useCacheAsideStategy();
-        System.out.println("=====================================================");
+        System.out.println("==============================================");
     }
 
     /**
@@ -103,7 +99,7 @@ public class App {
      * @param args input params
      * @return true if there is "--mongo" parameter in arguments
      */
-    private static boolean isDbMongo(String[] args) {
+    private static boolean isDbMongo(final String[] args) {
         for (String arg : args) {
             if (arg.equals(USE_MONGO_DB)) {
                 return true;
@@ -156,9 +152,15 @@ public class App {
         LOGGER.info("# CachingPolicy.BEHIND");
         appManager.initCachingPolicy(CachingPolicy.BEHIND);
 
-        var userAccount3 = new UserAccount("003", "Adam", "He likes food.");
+        var userAccount3 = new UserAccount("003",
-        var userAccount4 = new UserAccount("004", "Rita", "She hates cats.");
+                "Adam",
-        var userAccount5 = new UserAccount("005", "Isaac", "He is allergic to mustard.");
+                "He likes food.");
+        var userAccount4 = new UserAccount("004",
+                "Rita",
+                "She hates cats.");
+        var userAccount5 = new UserAccount("005",
+                "Isaac",
+                "He is allergic to mustard.");
 
         appManager.save(userAccount3);
         appManager.save(userAccount4);
@@ -166,7 +168,9 @@ public class App {
         LOGGER.info(appManager.printCacheContent());
         appManager.find("003");
         LOGGER.info(appManager.printCacheContent());
-        UserAccount userAccount6 = new UserAccount("006", "Yasha", "She is an only child.");
+        UserAccount userAccount6 = new UserAccount("006",
+                "Yasha",
+                "She is an only child.");
         appManager.save(userAccount6);
         LOGGER.info(appManager.printCacheContent());
         appManager.find("004");
@@ -181,9 +185,15 @@ public class App {
         appManager.initCachingPolicy(CachingPolicy.ASIDE);
         LOGGER.info(appManager.printCacheContent());
 
-        var userAccount3 = new UserAccount("003", "Adam", "He likes food.");
+        var userAccount3 = new UserAccount("003",
-        var userAccount4 = new UserAccount("004", "Rita", "She hates cats.");
+                "Adam",
-        var userAccount5 = new UserAccount("005", "Isaac", "He is allergic to mustard.");
+                "He likes food.");
+        var userAccount4 = new UserAccount("004",
+                "Rita",
+                "She hates cats.");
+        var userAccount5 = new UserAccount("005",
+                "Isaac",
+                "He is allergic to mustard.");
         appManager.save(userAccount3);
         appManager.save(userAccount4);
         appManager.save(userAccount5);

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

@@ -29,28 +29,41 @@ import com.iluwatar.caching.database.DbManager;
 import lombok.extern.slf4j.Slf4j;
 
 /**
- * AppManager helps to bridge the gap in communication between the main class and the application's
+ * AppManager helps to bridge the gap in communication between the main class
- * back-end. DB connection is initialized through this class. The chosen caching strategy/policy is
+ * and the application's back-end. DB connection is initialized through this
- * also initialized here. Before the cache can be used, the size of the cache has to be set.
+ * class. The chosen  caching strategy/policy is also initialized here.
- * Depending on the chosen caching policy, AppManager will call the appropriate function in the
+ * Before the cache can be used, the size of the  cache has to be set.
- * CacheStore class.
+ * Depending on the chosen caching policy, AppManager will call the
+ * appropriate function in the CacheStore class.
  */
 @Slf4j
 public class AppManager {
-
+  /**
+   * Caching Policy.
+   */
   private static CachingPolicy cachingPolicy;
+  /**
+   * Database Manager.
+   */
   private final DbManager dbManager;
+  /**
+   * Cache Store.
+   */
   private final CacheStore cacheStore;
 
-  public AppManager(DbManager dbManager) {
+  /**
-    this.dbManager = dbManager;
+   * Constructor.
-    this.cacheStore = new CacheStore(dbManager);
+   * @param newDbManager database manager
+   */
+  public AppManager(final DbManager newDbManager) {
+    this.dbManager = newDbManager;
+    this.cacheStore = new CacheStore(newDbManager);
   }
 
   /**
-   * Developer/Tester is able to choose whether the application should use MongoDB as its underlying
+   * Developer/Tester is able to choose whether the application should use
-   * data storage or a simple Java data structure to (temporarily) store the data/objects during
+   * MongoDB as its underlying data storage or a simple Java data structure
-   * runtime.
+   * to (temporarily) store the data/objects during runtime.
    */
   public void initDb() {
      dbManager.connect();
@@ -58,8 +71,9 @@ public class AppManager {
 
   /**
    * Initialize caching policy.
+   * @param policy is a {@link CachingPolicy}
    */
-  public void initCachingPolicy(CachingPolicy policy) {
+  public void initCachingPolicy(final CachingPolicy policy) {
     cachingPolicy = policy;
     if (cachingPolicy == CachingPolicy.BEHIND) {
       Runtime.getRuntime().addShutdownHook(new Thread(cacheStore::flushCache));
@@ -69,10 +83,13 @@ public class AppManager {
 
   /**
    * Find user account.
+   * @param userId String
+   * @return {@link UserAccount}
    */
-  public UserAccount find(String userId) {
+  public UserAccount find(final String userId) {
     LOGGER.info("Trying to find {} in cache", userId);
-    if (cachingPolicy == CachingPolicy.THROUGH || cachingPolicy == CachingPolicy.AROUND) {
+    if (cachingPolicy == CachingPolicy.THROUGH
+            || cachingPolicy == CachingPolicy.AROUND) {
       return cacheStore.readThrough(userId);
     } else if (cachingPolicy == CachingPolicy.BEHIND) {
       return cacheStore.readThroughWithWriteBackPolicy(userId);
@@ -84,8 +101,9 @@ public class AppManager {
 
   /**
    * Save user account.
+   * @param userAccount {@link UserAccount}
    */
-  public void save(UserAccount userAccount) {
+  public void save(final UserAccount userAccount) {
     LOGGER.info("Save record!");
     if (cachingPolicy == CachingPolicy.THROUGH) {
       cacheStore.writeThrough(userAccount);
@@ -98,25 +116,33 @@ public class AppManager {
     }
   }
 
+  /**
+   * Returns String.
+   * @return String
+   */
   public String printCacheContent() {
     return cacheStore.print();
   }
 
   /**
    * Cache-Aside save user account helper.
+   * @param userAccount {@link UserAccount}
    */
-  private void saveAside(UserAccount userAccount) {
+  private void saveAside(final UserAccount userAccount) {
     dbManager.updateDb(userAccount);
     cacheStore.invalidate(userAccount.getUserId());
   }
 
   /**
    * Cache-Aside find user account helper.
+   * @param userId String
+   * @return {@link UserAccount}
    */
-  private UserAccount findAside(String userId) {
+  private UserAccount findAside(final String userId) {
     return Optional.ofNullable(cacheStore.get(userId))
         .or(() -> {
-          Optional<UserAccount> userAccount = Optional.ofNullable(dbManager.readFromDb(userId));
+          Optional<UserAccount> userAccount =
+                  Optional.ofNullable(dbManager.readFromDb(userId));
           userAccount.ifPresent(account -> cacheStore.set(userId, account));
           return userAccount;
         })

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

@@ -3,14 +3,38 @@ package com.iluwatar.caching.database;
 import com.iluwatar.caching.UserAccount;
 
 /**
- * <p>DBManager handles the communication with the underlying data store i.e. Database. It contains
+ * <p>DBManager handles the communication with the underlying data store i.e.
- * the implemented methods for querying, inserting, and updating data. MongoDB was used as the
+ * Database. It contains the implemented methods for querying, inserting,
- * database for the application.</p>
+ * and updating data. MongoDB was used as the database for the application.</p>
  */
 public interface DbManager {
+    /**
+     * Connect to DB.
+     */
     void connect();
+
+    /**
+     * Read from DB.
+     * @param userId {@link String}
+     * @return {@link UserAccount}
+     */
     UserAccount readFromDb(String userId);
+    /**
+     * Write to DB.
+     * @param userAccount {@link UserAccount}
+     * @return {@link UserAccount}
+     */
     UserAccount writeToDb(UserAccount userAccount);
+    /**
+     * Update record.
+     * @param userAccount {@link UserAccount}
+     * @return {@link UserAccount}
+     */
     UserAccount updateDb(UserAccount userAccount);
+    /**
+     * Update record or Insert if not exists.
+     * @param userAccount {@link UserAccount}
+     * @return {@link UserAccount}
+     */
     UserAccount upsertDb(UserAccount userAccount);
 }

caching/src/main/java/com/iluwatar/caching/database/package-info.java

@@ -0,0 +1,4 @@
+/**
+ * Database classes
+ */
+package com.iluwatar.caching.database;

caching/src/main/java/com/iluwatar/caching/package-info.java

@@ -0,0 +1,24 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.caching;