Wipro Associate Java Developer Interview Questions and Answers

A sequence was provided: 4181, 2684, 1597, 987, 610.
first 2 are given and write code for other value calculation using java 8

The second question required writing a reverse of a palindrome using both Java 8 streams. I was able to successfully write both and clear the first round.

Q1. Interviewer was himself not knowing anything as it was walkin drive he was sitting infront of me and checking questions on phone Introduction that he inturrepted in between when I was introducing myself
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Q2. What are the features of Java 17, specifically related to sealed classes, including their syntax and necessity, along with the potential errors encountered when invoking a sealed class?
Ans. 
Java 17 introduces sealed classes to restrict inheritance and improve code maintainability.
• Sealed classes are declared using the 'sealed' keyword followed by the permitted subclasses.

• Subclasses of a sealed class must be either final or sealed themselves.

• Errors may occur when trying to extend a sealed class with a non-permitted subclass.
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Q3. Java 8 feathers stream api, functional interface, Intermittent operator ,Ternary operator, Prediction,Bi predicate. Answered all successfully
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Q4. Draw low level design of implementation of notify me if item is back in stock in a ecommerce application
Ans. 
Implementation of 'notify me if item is back in stock' feature in an ecommerce application
• Create a database table to store user notifications for out-of-stock items

• Implement a service to check item availability and send notifications to subscribed users

• Provide a user interface for users to subscribe to notifications for specific items
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Q5. All design patterns which I know. Asked me to implement adapter pattern on paper
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Q6. Then given a problem that concurrent way perform operation on excell to decrease the response time
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Q1. API Gateway implementation
Ans. 
API Gateway implementation is a centralized service that routes, manages, and secures API calls.
• API Gateway acts as a single entry point for all API calls

• It can handle authentication, rate limiting, caching, and request/response transformations

• Examples include AWS API Gateway, Apigee, Kong
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Q2. Circuit breaker implementation
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Circuit breaker is a design pattern used to prevent system overload by temporarily stopping requests to a failing service.
• Circuit breaker monitors requests to a service and opens when the service fails repeatedly.

• It helps prevent cascading failures and allows the system to gracefully degrade.

• Once the circuit breaker is open, it can periodically check if the service has recovered before allowing requests again.
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Q3. What is deadlock? How to avoid it?
Ans. 
Deadlock is a situation in which two or more processes are unable to proceed because each is waiting for the other to release a resource.
• Avoid circular wait by ensuring processes request resources in the same order.

• Prevent hold and wait by requiring processes to request all needed resources at once.

• Implement a timeout mechanism to break potential deadlocks.

• Use resource allocation graphs to detect and prevent deadlocks.

• ...read more
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Q4. Explain equals() method
Ans. 
The equals() method is used to compare the contents of two objects for equality.
• The equals() method is a method of the Object class in Java.

• It is used to compare the contents of two objects for equality.

• The default implementation of equals() in the Object class compares memory addresses, so it is often overridden in custom classes to compare content.

• Example: String class overrides equals() method to compare the content
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Q5. How mongodb was integrated in your application?
Ans. 
MongoDB was integrated in the application by using the official Java driver and configuring connection settings.
• Used the official MongoDB Java driver to interact with the database

• Configured connection settings such as host, port, database name, and authentication credentials

• Implemented CRUD operations using MongoDB Java driver methods

• Utilized MongoDB aggregation framework for complex queries
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Q6. What is hibernate?
Ans. 
Hibernate is an open-source Java framework that simplifies the development of database interactions in Java applications.
• Hibernate is an Object-Relational Mapping (ORM) tool that maps Java objects to database tables.

• It provides a way to perform database operations using Java objects instead of writing SQL queries.

• Hibernate handles the mapping of Java classes to database tables and vice versa, as well as the generation ...read more
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Q7. Runnable vs Callable interface
Ans. 
Runnable is a functional interface with a single run() method, while Callable is a functional interface with a single call() method.
• Runnable is used for tasks that do not return a result, while Callable is used for tasks that return a result.

• Callable can throw checked exceptions, while Runnable cannot.

• Callable returns a Future object, which can be used to retrieve the result of the computation.

• Example: Runnable - execu...read more
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Q8. Which type of data is returned by Callable interface?
Ans. 
The Callable interface in Java returns a Future object.
• Callable interface returns a Future object which represents the result of a computation that may not be available yet.

• The Future object can be used to retrieve the result of the computation, check if it is done, or cancel the computation.

• Example: Callable<Integer> task = () -> { return 42; }
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Q9. HashMap internal working
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Q10. Concurrent HashMap internal working
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Q11. How to monitor health of your application?
Ans. 
Monitor application health using metrics, logs, alerts, and performance monitoring tools.
• Use monitoring tools like Prometheus, Grafana, or New Relic to track key metrics such as CPU usage, memory usage, response times, and error rates.

• Implement logging to record important events and errors in your application. Use tools like ELK stack (Elasticsearch, Logstash, Kibana) for log analysis.

• Set up alerts to notify you of any...read more
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Q12. How to call an API in a Microservice architecture?
Ans. 
To call an API in a Microservice architecture, use HTTP requests or messaging protocols like gRPC.
• Use HTTP requests to communicate between microservices

• Implement RESTful APIs for easy integration

• Leverage messaging protocols like gRPC for efficient communication

• Consider using service discovery mechanisms for dynamic API calls
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Q13. Explain Profiles
Ans. 
Profiles in Java are configurations that define the capabilities of a Java platform.
• Profiles allow developers to target specific types of devices or applications.

• They help in reducing the size of the Java runtime environment by including only the necessary APIs.

• Examples include Java SE Embedded Profile for embedded devices and Java SE Compact Profile for resource-constrained environments.
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Q14. What is OpenFeign, and how is it used in microservices architecture?
Ans. 
OpenFeign is a declarative web service client used to simplify the process of making HTTP requests in microservices architecture.
• OpenFeign allows developers to define RESTful web services as interfaces and automatically generate the necessary implementation code.

• It integrates seamlessly with Spring Cloud and other microservices frameworks to facilitate communication between services.

• OpenFeign supports features like loa...read more
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Q15. What is the implementation process for service registry and discovery?
Ans. 
Service registry and discovery involves registering services and allowing clients to discover and connect to them.
• Implement a service registry where services can register themselves with metadata

• Use a service discovery mechanism for clients to find and connect to services

• Implement health checks to ensure services are available and healthy

• Use a load balancer to distribute traffic among multiple instances of a service
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Q16. What are Spring boot actuators?
Ans. 
Spring Boot Actuators are built-in tools that provide insight into the running application.
• Actuators expose various endpoints to monitor and manage the application.

• They can be used to check health, metrics, environment details, and more.

• Examples include /actuator/health, /actuator/metrics, and /actuator/env.
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Q17. Synchronous vs Asynchronous communication
Ans. 
Synchronous communication is blocking, while asynchronous communication is non-blocking.
• Synchronous communication waits for a response before continuing, while asynchronous communication does not wait.

• Examples of synchronous communication include traditional function calls, while examples of asynchronous communication include callbacks and promises.

• Synchronous communication can lead to performance issues if there are d...read more
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Q18. Explain Synchronized keyword
Ans. 
Synchronized keyword is used in Java to control access to shared resources by multiple threads.
• Synchronized keyword can be applied to methods or code blocks to ensure only one thread can access the synchronized code at a time.

• It prevents race conditions and ensures thread safety by creating a lock on the object or class.

• Example: synchronized void myMethod() { // synchronized code block }
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Q19. What are the consequences of excessively using synchronized blocks and methods in Java?
Ans. 
Excessive use of synchronized blocks and methods in Java can lead to performance issues and potential deadlocks.
• Decreased performance due to increased contention for locks

• Potential deadlocks if multiple threads are waiting for each other to release locks

• Increased complexity and difficulty in debugging and maintaining code

• Use synchronized sparingly and consider alternatives like ConcurrentHashMap or Lock interface
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Q20. How can you determine the number of threads needed for your application?
Ans. 
The number of threads needed for an application can be determined based on factors like the type of tasks, hardware resources, and performance requirements.
• Consider the type of tasks your application needs to perform - CPU-bound tasks may benefit from more threads, while I/O-bound tasks may not.

• Take into account the hardware resources available - more threads may be beneficial on a multi-core processor compared to a si...read more
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Q21. Explain Executor framework
Ans. 
Executor framework is a framework in Java that provides a way to manage and execute tasks asynchronously.
• Allows for managing thread execution in a more efficient way

• Provides a way to decouple task submission from task execution

• Supports various types of executors like ThreadPoolExecutor and ScheduledExecutorService

• Helps in handling tasks concurrently and asynchronously
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Q22. Explain BlockingQueue
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BlockingQueue is an interface in Java that represents a queue which supports operations that wait for the queue to become non-empty when retrieving an element and wait for space to become available in the queue when adding an element.
• BlockingQueue is part of the java.util.concurrent package.

• It is used for implementing producer-consumer scenarios where multiple threads are involved.

• Methods like put() and take() are used...read more
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Q1. Why did you leave your previous company?
Ans. 
Seeking new challenges and opportunities for growth.
• Desire for career advancement

• Looking for new challenges

• Seeking better work-life balance

• Company restructuring or downsizing

• Relocation to a new area
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Q2. Other basic questions asked regarding the relevant skills and technologies I have worked with.
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Q1. What improvements to interfaces were introduced in Java 8 that were missing in Java 7, specifically regarding static and default methods?
Ans. 
Java 8 introduced static and default methods in interfaces, allowing for method implementation and code reusability.
• Java 8 introduced static methods in interfaces, allowing for method implementation directly in the interface itself.

• Default methods were also introduced in Java 8, enabling interfaces to have method implementations without affecting implementing classes.

• Static methods in interfaces can be called using the...read more
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Q2. Explain internal working of HashMap ? How to synchronize it ?
Ans. 
HashMap is a data structure that stores key-value pairs and uses hashing to efficiently retrieve values.
• HashMap uses an array of linked lists to store key-value pairs.

• When a key-value pair is added, the key is hashed to determine the index in the array where it will be stored.

• If multiple keys hash to the same index, a linked list is used to handle collisions.

• To synchronize a HashMap, you can use the synchronizedMap() m...read more
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Q3. Given a list of employees with their ratings, how can you sort the employees based on their ratings using the Java 8 Streaming API?
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Q4. Will the program compile if the parent class throws a runtime exception while the child class throws an arithmetic exception?
Ans. 
No, the program will not compile if the parent class throws a runtime exception while the child class throws an arithmetic exception.
• In Java, if a parent class method throws a checked exception, the child class method can only throw the same exception or its subclasses.

• ArithmeticException is an unchecked exception, so if the parent class throws a checked exception and the child class throws an unchecked exception, the ...read more
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Q5. In a Spring Boot application with two databases, how can you configure JDBC to specify which database to use?
Ans. 
Configure JDBC in Spring Boot to specify which database to use
• Define multiple DataSource beans in the configuration class

• Use @Primary annotation to specify the primary DataSource

• Use @Qualifier annotation to specify the secondary DataSource

• Inject the DataSource beans where needed in the application
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Q6. How to use a jetty server in your spring boot application ?
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To use a Jetty server in a Spring Boot application, you can configure it as a dependency and customize its settings.
• Add Jetty server dependency in your pom.xml file

• Exclude Tomcat server dependency if it's included by default in Spring Boot

• Configure Jetty server settings in application.properties or application.yml file

• Example: Add Jetty dependency - <dependency> <groupId>org.springframework.boot</groupId...read more
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Q7. Difference between @RequestParam and @PathVariable ?
Ans. 
RequestParam is used to extract query parameters from the URL, while PathVariable is used to extract values from the URI path.
• RequestParam is used for query parameters in the URL, while PathVariable is used for values in the URI path.

• RequestParam is optional, while PathVariable is required.

• RequestParam is used with the @RequestParam annotation, while PathVariable is used with the @PathVariable annotation.

• Example: @Requ...read more
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Q8. How would you handle a scenario where one microservice is awaiting a response from another microservice that is taking an extended time to respond?
Ans. 
I would implement timeout mechanisms and retries to handle the scenario of one microservice awaiting a response from another microservice taking an extended time.
• Implement timeout mechanisms in the calling microservice to limit the waiting time for a response.

• Set up retry logic to automatically resend the request to the slow microservice if no response is received within the specified timeout period.

• Use circuit breaker...read more
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It is all concepts for communication skills

This is some role of the coding ,for example: java,html,css,javascript like that coding

Q1. Subject based questions they are asking
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Q1. Overall details asking them
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This is observed the skills

Q1. Given an array {1, 2, 1, 4, 5, 4, 8, 7}, how can you use Streams to remove duplicates while retaining only the even numbers?
Ans. 
Use Streams to remove duplicates and retain only even numbers from an array.
• Convert the array to a stream using Arrays.stream()

• Use distinct() to remove duplicates

• Filter out odd numbers using filter()

• Collect the result using collect(Collectors.toList())
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Q2. What is the use of Static and final when you will use Static methods
Ans. 
Static methods can be accessed without creating an instance of the class, while final keyword makes the method unchangeable.
• Static methods belong to the class itself, not to any specific instance

• Final keyword ensures that the method cannot be overridden in subclasses

• Static methods are commonly used for utility methods that do not require access to instance variables

• Example: Math class in Java has static methods like Ma
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Q3. What is the difference between @restController and @controller Annotation
Ans. 
The @RestController annotation is used to define RESTful web services while @Controller annotation is used to define MVC controller.
• RestController is a specialized version of Controller used for RESTful web services

• RestController eliminates the need for @ResponseBody annotation

• Controller is used for traditional MVC controller functionality

• RestController returns data directly without needing to go through a view resolve...read more
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Q4. What is microservices why we use it
Ans. 
Microservices are a software development technique where applications are composed of small, independent services that communicate with each other.
• Microservices allow for easier scalability and maintenance of complex applications.

• Each service in a microservices architecture can be developed, deployed, and scaled independently.

• Microservices promote flexibility and agility in software development.

• Examples of companies us...read more
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Q1. Project based questions
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Q2. Scenario based question (multithreading and caching related scenarios were asked to me)
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Q3. One coding challenge
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Q1. Different types of streams based questions
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Q2. Collection , competable future, java 8 features
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Q1. Transactions in springboot
Ans. 
Transactions in Spring Boot manage database operations as a single unit of work to ensure data integrity.
• Spring Boot provides support for declarative transaction management using @Transactional annotation.

• Transactions can be configured at class or method level.

• Transactions can be rolled back in case of exceptions to maintain data consistency.

• Example: @Transactional annotation on a service method ensures that all databa...read more
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Q2. Difference between arraylist and linked list

Ans. 

ArrayList is resizable array implementation, LinkedList is doubly linked list implementation.

• ArrayList uses dynamic array to store elements, LinkedList uses doubly linked list.

• ArrayList is faster for accessing elements by index, LinkedList is faster for adding/removing elements.

• Example: ArrayList arrList = new ArrayList<>(); LinkedList linkedList = new LinkedList<>();

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