Carelan Java Support Engineer Interview Questions, Process, and Tips

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. Previous projects
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Q2. Spring boot annotations
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Q1. Coding round swap two numbers without using third variable
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Q2. Salary expectations
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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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Q1. Create one Spring boot controller from end to end. No need to create a spring boot project we just want to see the structure and end to end implementation.
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Q2. Write a java 8 program to get the characters from a string whose count is 2 or more than 2 e.g. input: baseball , output: b, a, l.
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Q3. Why you left your previous organization.
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Q4. What is the functional interface
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Q5. What are the OOPS concepts. and some questions related to inheritance.
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Q6. Asked about the project mentioned in CV (Client project) and asked its architecture.
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Q7. Various SQL join types
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Q1. Are you ready to relocate to job location
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Q2. Why are you leaving your previous organization.
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Q3. Expectation about salary
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Q1. How much exp in docker?
Ans. 
I have 2 years of experience working with Docker in various projects.
• 2 years of experience working with Docker in various projects

• Proficient in creating Docker containers, managing images, and orchestrating containers using Docker Compose

• Familiar with Docker Swarm and Kubernetes for container orchestration

• Experience in troubleshooting Docker-related issues and optimizing container performance
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Q2. Do you have exp in Kubernetes?
Ans. 
Yes, I have experience in Kubernetes.
• I have worked on deploying and managing applications on Kubernetes clusters.

• I am familiar with creating and managing Kubernetes resources such as pods, deployments, services, and ingresses.

• I have experience in using tools like kubectl and Helm for interacting with Kubernetes clusters.

• I have implemented CI/CD pipelines using Kubernetes for automated deployment and scaling of applicat
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Q3. What is OOP?
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OOP stands for Object-Oriented Programming, a programming paradigm based on the concept of objects.
• OOP focuses on creating objects that contain data and methods to manipulate that data.

• Encapsulation, inheritance, and polymorphism are key principles of OOP.

• Examples of OOP languages include Java, C++, and Python.
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Q4. Types of polymorphism
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Polymorphism in Java refers to the ability of a method to do different things based on the object it is acting upon.
• Types of polymorphism in Java include method overloading and method overriding.

• Method overloading is when multiple methods have the same name but different parameters.

• Method overriding is when a subclass provides a specific implementation of a method that is already defined in its superclass.
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Q5. Thread in java
Ans. 
Threads in Java allow multiple tasks to run concurrently within a single program.
• Threads are lightweight sub-processes that share the same memory space.

• They are used to improve performance by allowing tasks to run simultaneously.

• Examples include creating a new thread using the Thread class or implementing the Runnable interface.
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Q6. Knowledge in which spring modules
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Q7. What is spring profile
Ans. 
Spring profile is a way to segregate parts of your application configuration and make it only available in certain environments.
• Spring profiles allow you to define different configurations for different environments such as development, testing, and production.

• You can use @Profile annotation to specify which beans should be loaded based on the active profile.

• Profiles can be activated in various ways such as through app...read more
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Q8. What is @PreAuthorize and @PostAuthorize
Ans. 
Annotations used in Spring Security to apply authorization rules before and after a method is called.
• Used in Spring Security to define authorization rules

• @PreAuthorize is used to apply authorization rules before a method is called

• @PostAuthorize is used to apply authorization rules after a method is called

• Both annotations support SpEL expressions for defining rules
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Q1. Java 8 , java 11 and java 17 features?
Ans. 
Java 8 introduced lambda expressions, Java 11 added local-variable syntax for lambda parameters, and Java 17 included sealed classes and pattern matching.
• Java 8 introduced lambda expressions for functional programming.

• Java 11 added local-variable syntax for lambda parameters to simplify code.

• Java 17 included sealed classes to restrict inheritance and pattern matching for instanceof checks and type casts.
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Q2. Dispatcher servlet, design patterns
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Q3. @SpringbootApplication annotation, actuators
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Q4. String Coding question with java 8 features such as lambda function and stream api
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Q5. Number of words in a string
Ans. 
Count the number of words in a given string.
• Split the string by spaces and count the number of resulting elements.

• Handle edge cases like multiple spaces or empty strings.

• Consider punctuation marks as part of words unless specified otherwise.
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Q6. Microservice design patterns
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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
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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. What are intermediate and terminal operations
Ans. 
Intermediate operations transform the elements of a stream, while terminal operations produce a result or side-effect.
• Intermediate operations include map, filter, sorted, distinct, etc.

• Terminal operations include forEach, collect, reduce, count, etc.

• Intermediate operations are lazy and do not execute until a terminal operation is called.

• Terminal operations trigger the processing of the stream and produce a result.
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Q2. Predefined functional interface
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Q3. Ways to create Thread
Ans. 
Ways to create Thread in Java
• Extending the Thread class

• Implementing the Runnable interface

• Using Executor framework
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