BNYM QC

Question 1

1. What is the new feature in Java 11 that allows the type of lambda parameters to be inferred using the ‘var’ keyword?

Answer 1

• “Local-Variable” Syntax

Question 2

2. What new String methods were introduced?

Answer 2

• isBlank()
• lines()
• strip()
• stripLeading()
• stripTrailing()
• repeat()

Question 3

3. What Collection related method was introduced?

Answer 3

• Collection.toArray(IntFunction)
• It is a default method added to the Collection Interface

Question 4

4. What other notable Java 11 features have been added or changed?

Answer 4

• New File Methods
• Not Predicate Method
• HTTPClient
• Can directly run Java source files with “java” CLI tool

Question 5

5. What is Pattern Matching? Which version of Java introduced it?

Answer 5

• Used to test if an object has a particular structure and if so, then that data is extracted from that object
• Introduced in Java 14
  -Added support for switch expressions

Question 6

6. What improvements did Java 17 add to Garbage Collection?

Answer 6

• Parallel GC is much faster
• Improved heap allocation to the G1GC
• Introduced ZGC, which provides low latency and minimal pauses

Question 7

7. What is the purpose of the Java Platform Module System (JPMS)?

Answer 7

• To encapsulate Java code into modules, making it easy to maintain large scale Java applications.

Question 8

8. What is a module in JPMS? How is it different from a regular Java package?

Answer 8

• A module is a unit of code that contains Java packages and resources.
• It’s different from a Java package because it provides stronger encapsulation, which means only the specified parts of a module are accessible, and the rest remain hidden.

Question 9

9. What is a module descriptor in JPMS? What information does it contain?

Answer 9

• A file that describes the content and dependencies of a module.
• It contains information such as the module name, packages it exports which make it accessible to other modules, and other optional configurations.

Question 10

10. What are the benefits of using JPMS in terms of security and performance?

Answer 10

• Security, JPMS enforces strong encapsulation, which helps prevent unauthorized access to internal code.
• Performance, JPMS allows Java runtime to analyze and optimize module dependencies, resulting in more efficient loading of code.

Question 11

11. What is the debugger?

Answer 11

• A tool used to identify and resolve issues or bugs in software code.
• It allows us to step through code line by line, inspect variables, and observe the program’s behavior in order to understand and fix any problem.

Question 12

12. What is a breakpoint?

Answer 12

• An international stopping point at a specific line of code
• By stopping the program’s execution the developer can inspect variables at the given point.

Question 13

13. Step Into vs Step Over vs Step Return?

Answer 13

• Step Into goes inside the methods used in the current line; else it proceeds to the next line.
• Step Over operation process the current line and proceeds to the next line.
• Step Return operation finishes the current method and takes us back to the calling method.

Question 14

14. What is variable inspection?

Answer 14

• Returns the value of any method that is called in the current context.

Question 15

15. Difference between a Collection and a Stream? What are the benefits of Stream API?

Answer 15

• Collection is a framework that provides architecture to store and manipulate a group of objects, providing many interfaces such as set, list, queue, dequeue and classes such as ArrayList, LinkedList and more.
• Stream is a sequence of objects that support various methods which can be pipelined to produce the desired result.
• Benefits: Streams do not change the original data structure, succinctly express sophisticated behavior.

Question 16

16. What is an intermediate operation? Can you give any examples?

Answer 16

• Lazily executed operation that returns a stream
• Examples: Map, Filter, Sorted

Question 17

17. What’s a terminal operation? Can you give any examples?

Answer 17

• Mark the end of the stream and return the result
• Examples: Collect, forEach, Reduce, findAny, Min

Question 18

18. Difference between H2 and RDBMS?

Answer 18

• H2 is a specific database management system known for its lightweight nature and in-memory capabilities. It is often used for smaller applications and testing scenarios.
• RDBMS is a class of database management systems that follow the relational model and are used in a wide range of applications, from small-scale to enterprise-level systems.

Question 19

19. What is a transaction?

Answer 19

• A unit of work that consists of multiple database operations, grouped together to ensure ACID properties.

Question 20

20. Purpose of XA (eXtended Architecture) in transaction management?

Answer 20

• Coordinates the transactional behavior of resources, ensuring that either all the resources commit their changes or all the changes are rolled back in case of any failure.

Question 21

21. What is two-phase commit protocol (in distrubuted transactions)?

Answer 21

• Prepare phase: The transaction manager ask each RM to prepare for committing the transaction. The RM then performs its local transaction operation and prepares to commit or rollback.
• Commit phase: The transaction manager sends a commit request to each RM if they all respond with a successful prepare status. If any RM encounters an error during the prepare phase, the transaction manager sends a rollback requests to all the RMs for them to rollback the changes made during the transaction.

Question 22

22. What is the role of a JTA Transaction Manager in distributed transactions?

Answer 22

• Java Transaction API Manager is responsible for coordinating and managing transactions across multiple resources (such as databases, messages queues, and other transactional resources) in a distributed environment. It ensures the ACID properties of transactions.

Question 23

23. Global vs Local Transaction?

Answer 23

• Global transactions involve multiple resources that participate in a single distributed transaction. Typically managed by a transaction manager using protocols like the Two-phase commit.
• Local Transaction involves a single resource, typically managed by a resource manager.

Question 24

24. What is sorting and Pagination?

Answer 24

• Sorting: Arranging data in a specific order based on one or more criteria.
• Pagination: Divides a large dataset or list of items into smaller, discrete pages or chunks. Improves performance by reducing the amount of data transferred and rendered at once.

Question 25

25. Transaction Management?

Answer 25

- The process of ensuring the reliable and consistent execution of transactions in a system; ensure ACID properties. - Involves Transaction manager, Resource manager, and Transaction context.

Question 26

26. What is @Transactional?

Answer 26

- Metadata that specifies the semantics of the transaction on a method, allowing us to make changes to the database and automatically rollback when there is an issue. - We can configure propagation type, isolation level, timeout, readonly, and rollback rules

Question 27

27. What are the different Transaction propagation options? What do they do?

Answer 27

- Propagation.REQUIRES: * If a transaction exists, the method participates in that transaction * If no transaction exists, a new transaction is created - Propagation.SUPPORTS: * Method supports a transaction if one exists * If no transaction exists, the method executes non-transactionally - Propagation.MANDATORY: * The method requires a transaction to be already active * If no transaction exists, an exception is thrown - Propagation.REQUIRES_NEW: * The method always starts a new transaction * If a transaction exists, it is suspended until the new transaction completes * Once the new transaction is complete, the suspended transaction resumes - Propagation.NOT_SUPPORTED: * The method executes non-transactionally * If a transaction exists, it is suspended until the new transaction completes * Once the new transaction is complete, the suspended transaction resumes - Propagation.NEVER: * The method executes non-transactionally * If a transaction exists, an exception is thrown - Propagation.NESTED: * The method executes within a nested transaction * If a transaction exists, a new nested transaction is started * If no transaction exists, a new transaction is started

Question 28

28. What are the different isolation levels? What do they do?

Answer 28

- Isolation.DEFAULT: * The actual isolation level will be determined by the database’s default behavior - Isolation.READ_UNCOMMITTED: * Allows dirty reads, non-repeatable reads, and phantom reads * Provides the lowest level of isolation - Isolation.READ-COMMITTED: * Does not allow dirty reads but allows non-repeatable reads and phantom reads * This is the default isolation level in many database systems - Isolation.REPEATABLE_READ: * Prevents dirty reads and non-repeatable reads but allows phantom reads * Guarantees a consistent snapshot of data throughout a transaction. - Isolation.SERIALIZABLE: * Provides the highest level of isolation * Prevents dirty reads, non-repeatable reads, and phantom reads by acquiring locks on accessed data

Question 29

29. JPA vs SQL?

Answer 29

- JPA is a Java specification that provides a standardized API for Object-Relational Mapping (ORM) - SQL is a programming language designed for working with relational databases

Question 29

29. JPA vs SQL?

Answer 29

- JPA is a Java specification that provides a standardized API for Object-Relational Mapping (ORM) - SQL is a programming language designed for working with relational databases

Question 30

30. What are the core interfaces in Hibernate?

Answer 30

- Session, SessionFactory, and Configuration Interface are mandatory - Transaction, Query, and Criteria Interface