clearing Sonar Blockers (#1633)

* 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>

Author: ohbus

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

@@ -67,7 +67,7 @@ public DbCustomerDao(DataSource dataSource) {
  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 boolean isLock() {
 
  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 HotelDaoImpl(DataSource dataSource) {
  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) {