docs: update .all-contributorsrc [skip ci]

* update gitignore

.checkstyle files are being tracked which should not be

* NOSONAR for statement

excluded from SONAR analysis as it is already dealt using functional approach

https://sonarcloud.io/project/issues?id=iluwatar_java-design-patterns&issues=AW8FwRBhm8eoEVQR-x0f&open=AW8FwRBhm8eoEVQR-x0f

* achieved thread safety with lazy initialization

https://sonarcloud.io/project/issues?fileUuids=AXb6t0PKusn4P8Tm-LmM&id=iluwatar_java-design-patterns&open=AXb6t19yusn4P8Tm-Lmo&resolved=false

* remove double checked locking and initialize before using

https://sonarcloud.io/project/issues?fileUuids=AXb6t0PKusn4P8Tm-LmK&id=iluwatar_java-design-patterns&open=AXb6t19qusn4P8Tm-Lmk&resolved=false

* NOSONAR for the line

https://sonarcloud.io/project/issues?id=iluwatar_java-design-patterns&issues=AXPd3iSe46HRSze7cz3D&open=AXPd3iSe46HRSze7cz3D

Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com>

.all-contributorsrc

@@ -1386,6 +1386,15 @@
       "contributions": [
         "code"
       ]
+    },
+    {
+      "login": "byoungju94",
+      "name": "byoungju94",
+      "avatar_url": "https://avatars.githubusercontent.com/u/42516378?v=4",
+      "profile": "https://github.com/byoungju94",
+      "contributions": [
+        "code"
+      ]
     }
   ],
   "contributorsPerLine": 4,

README.md

@@ -10,7 +10,7 @@
 [![Coverage](https://sonarcloud.io/api/project_badges/measure?project=iluwatar_java-design-patterns&metric=coverage)](https://sonarcloud.io/dashboard?id=iluwatar_java-design-patterns)
 [![Join the chat at https://gitter.im/iluwatar/java-design-patterns](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/iluwatar/java-design-patterns?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 <!-- ALL-CONTRIBUTORS-BADGE:START - Do not remove or modify this section -->
-[![All Contributors](https://img.shields.io/badge/all_contributors-152-orange.svg?style=flat-square)](#contributors-)
+[![All Contributors](https://img.shields.io/badge/all_contributors-153-orange.svg?style=flat-square)](#contributors-)
 <!-- ALL-CONTRIBUTORS-BADGE:END -->
 
 <br/>
@@ -303,6 +303,9 @@ This project is licensed under the terms of the MIT license.
     <td align="center"><a href="https://github.com/demirhalil"><img src="https://avatars1.githubusercontent.com/u/22895118?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Halil Demir</b></sub></a><br /><a href="#translation-demirhalil" title="Translation">🌍</a></td>
     <td align="center"><a href="https://github.com/rohit10000"><img src="https://avatars.githubusercontent.com/u/20845565?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Rohit Singh</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=rohit10000" title="Code">💻</a></td>
   </tr>
+  <tr>
+    <td align="center"><a href="https://github.com/byoungju94"><img src="https://avatars.githubusercontent.com/u/42516378?v=4?s=100" width="100px;" alt=""/><br /><sub><b>byoungju94</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=byoungju94" title="Code">💻</a></td>
+  </tr>
 </table>
 
 <!-- markdownlint-restore -->

dao/src/main/java/com/iluwatar/dao/DbCustomerDao.java

@@ -67,7 +67,7 @@ public class DbCustomerDao implements CustomerDao {
   public Stream<Customer> getAll() throws Exception {
     try {
       var connection = getConnection();
-      var statement = connection.prepareStatement("SELECT * FROM CUSTOMERS");
+      var statement = connection.prepareStatement("SELECT * FROM CUSTOMERS"); // NOSONAR
       var resultSet = statement.executeQuery(); // NOSONAR
       return StreamSupport.stream(new Spliterators.AbstractSpliterator<Customer>(Long.MAX_VALUE,
           Spliterator.ORDERED) {

special-case/src/main/java/com/iluwatar/specialcase/Db.java

@@ -38,16 +38,13 @@ public class Db {
    *
    * @return singleton instance of Db class
    */
-  public static Db getInstance() {
+  public static synchronized Db getInstance() {
     if (instance == null) {
-      synchronized (Db.class) {
-        if (instance == null) {
-          instance = new Db();
-          instance.userName2User = new HashMap<>();
-          instance.user2Account = new HashMap<>();
-          instance.itemName2Product = new HashMap<>();
-        }
-      }
+      Db newInstance = new Db();
+      newInstance.userName2User = new HashMap<>();
+      newInstance.user2Account = new HashMap<>();
+      newInstance.itemName2Product = new HashMap<>();
+      instance = newInstance;
     }
     return instance;
   }

special-case/src/main/java/com/iluwatar/specialcase/MaintenanceLock.java

@@ -38,13 +38,9 @@ public class MaintenanceLock {
    *
    * @return singleton instance of MaintenanceLock
    */
-  public static MaintenanceLock getInstance() {
+  public static synchronized MaintenanceLock getInstance() {
     if (instance == null) {
-      synchronized (MaintenanceLock.class) {
-        if (instance == null) {
-          instance = new MaintenanceLock();
-        }
-      }
+      instance = new MaintenanceLock();
     }
     return instance;
   }
@@ -55,6 +51,6 @@ public class MaintenanceLock {
 
   public void setLock(boolean lock) {
     this.lock = lock;
-    LOGGER.info("Maintenance lock is set to: " + lock);
+    LOGGER.info("Maintenance lock is set to: ", lock);
   }
 }

transaction-script/src/main/java/com/iluwatar/transactionscript/HotelDaoImpl.java

@@ -49,7 +49,7 @@ public class HotelDaoImpl implements HotelDao {
   public Stream<Room> getAll() throws Exception {
     try {
       var connection = getConnection();
-      var statement = connection.prepareStatement("SELECT * FROM ROOMS");
+      var statement = connection.prepareStatement("SELECT * FROM ROOMS"); // NOSONAR
       var resultSet = statement.executeQuery(); // NOSONAR
       return StreamSupport.stream(new Spliterators.AbstractSpliterator<Room>(Long.MAX_VALUE,
           Spliterator.ORDERED) {