1) How do you achieve concurrency in your current job, and write code for it? 2) Write code for Rest API using Springboot, need to write Entity, Service, Repository, and Controller classes? 3)Volatile keywords, does it support synchronization? 4)Try with resources, do we need to close the connection after opening it using Try with resources? 5) Exception handling hierarchy?

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1) Concurrency is achieved using multithreading in Java. Use threads, executors, or synchronized blocks. Example: using ExecutorService to run multiple tasks concurrently.
2) Rest API in Springboot: Entity class defines database table, Service class contains business logic, Repository class interacts with database, Controller class handles HTTP requests.
3) Volatile keyword provides visibility guarantee but does not support synchronization. Use synchronized keyword for synchronization.
4) Try with resources automatically closes resources like connections. No need to manually close them.
5) Exception handling hierarchy in Java: Throwable -> Error (unchecked) and Exception (checked) -> RuntimeException (unchecked) and checked exceptions.

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