I was rejected in the first round itself and am unsure about the number of rounds. The interviewer was unprofessional; the interview felt like a question-and-answer session rather than a discussion.

Below are the questions asked:

• How to avoid duplicates in an ArrayList.
• What is the principle of microservices?
• How do you move an application to the cloud?
• When do we override equals and hashCode?
• Difference between HashMap and Hashtable.
• What error occurs when we add a duplicate key to a Map?
• Java 8 features.
• How to use streams with a List.
• How to implement pagination without a Page object?
• How to get an object from an ArrayList with 1 lakh objects?
• How to avoid duplicate objects without overriding equals and hashCode?
• When to choose RDBMS versus MongoDB?
• Which database is suited for transactional data, i.e., continuous addition?
• Difference between equals and ==.
• How many objects are created with new String("a") and new String("a")?
• Difference between Spring and Spring Boot.
• How to update Spring Boot versions?
• What happens internally when we use the new keyword?

I was rejected despite performing well and am unsure about the interviewer's expectations.

How to get an object from an ArrayList if we have 1 lakh objects?