Microservice interview Question Java coding interview questions part-9

#microservicestutorial #javamicrosoft #javainterviewquestions #java #javainterview #microservices #microservicios
1.Take an array and do squares of each number?
2.What is optimistic in java.
Ans:-Mechanism used in JPA to handle concurrent updates to the same entity.it aims to prevent conflicts by allowing multiple transaction to read and update same entity simultaneously.

Each entity that requires optimistic locking is annotated with @Version. This annotation marks a field or property that represents the version of the entity.
3.What are spring boot annotates
Ans:-@SpringBootApplication: This annotation is used to mark the main class of a Spring Boot application. It combines @Configuration, @EnableAutoConfiguration, and @ComponentScan annotations into a single convenient annotation.

@RestController: This annotation is used to define a class as a RESTful controller. It combines @Controller and @ResponseBody annotations, indicating that the methods in the class will handle HTTP requests and directly serialize the return values to the response body.
@RequestMapping: This annotation is used to map HTTP requests to specific methods in a controller. It defines the URL path and the HTTP method(s) that the method should handle.
@Autowired: This annotation is used to inject dependencies automatically. It can be applied to constructor parameters, fields, or setter methods.
@Service: This annotation is used to mark a class as a service component in the business logic layer. It is typically used in service classes that encapsulate business logic and interact with repositories or other services.

@Repository: This annotation is used to mark a class as a repository component in the persistence layer. It is typically used in classes that perform database operations, such as data access and manipulation.

@Configuration: This annotation is used to indicate that a class provides bean definitions and should be processed by the Spring container.

@ComponentScan: This annotation is used to specify the base packages for component scanning. It allows Spring to automatically discover and register beans in the specified packages.

@Value: This annotation is used to inject values from configuration properties or environment variables into fields or constructor parameters.

@Validated: This annotation is used to enable validation on method parameters or bean properties using validation annotations such as @NotNull, @NotBlank, etc.

4.volatile keyword in java
Ans:-The "volatile" keyword in Java is used to declare a variable whose value may be modified by multiple threads. It ensures that any read or write to the volatile variable is directly performed on the main memory, rather than using a thread's local cache. This guarantees that changes made by one thread to the volatile variable are visible to other threads immediately.

Key points about the "volatile" keyword:

Visibility: The use of "volatile" ensures that changes made to a volatile variable are visible to all threads. When a thread reads a volatile variable, it always sees the most up-to-date value.

Atomicity: The "volatile" keyword does not provide atomicity by itself. It only guarantees visibility. If multiple threads perform read-modify-write operations on a volatile variable concurrently, additional synchronization mechanisms (e.g., locks or atomic classes) should be used to ensure atomicity.

Ordering: The "volatile" keyword also establishes a happens-before relationship, meaning that any write to a volatile variable is guaranteed to happen before any subsequent read of that variable. This ensures proper ordering of operations across threads.

No synchronization: The "volatile" keyword does not acquire locks or block threads. It is a lighter-weight synchronization mechanism compared to using locks, but it has its limitations and is not a substitute for synchronization in all scenarios.

Common use cases for the "volatile" keyword include flags for signaling between threads or when implementing simple lock-free algorithms.

5.What is Stream API in java.
Ans:-The Stream API in Java provides a functional programming approach to process collections of data. It allows for concise and expressive code to perform operations like filtering, mapping, sorting, and aggregating data. Here are some key points about the Stream API:

Stream Creation: Streams can be created from various data sources, including collections, arrays, I/O channels, and generators. The Stream interface represents a sequence of elements.

Laziness: Streams support lazy evaluation, meaning that intermediate operations are not executed until a terminal operation is invoked. This allows for efficient processing by avoiding unnecessary computations.

Watch full Play list:-https://www.youtube.com/watch?v=mjfUBhJjhxM&list=PLZsXVwKkaRVvzOCQPuTuquF9YvI5jeqUp