Carelan Java Support Engineer Interview Questions, Process, and Tips

Q1. What improvements to interfaces were introduced in Java 8 that were missing in Java 7, specifically regarding static and default methods?
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Q2. Explain internal working of HashMap ? How to synchronize it ?
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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?
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Q5. In a Spring Boot application with two databases, how can you configure JDBC to specify which database to use?
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Q6. How to use a jetty server in your spring boot application ?
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Q7. Difference between @RequestParam and @PathVariable ?
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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?
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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
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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
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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
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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
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Q2. Predefined functional interface
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Q3. Ways to create Thread
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The first round was an interview conducted with a GENAI virtual bot.

Q1. Internal architecture of Spring boot, how enable autoconfiguration works
Ans. 
Spring Boot uses autoconfiguration to automatically configure the Spring application based on dependencies and properties.
• Spring Boot autoconfiguration is achieved through @EnableAutoConfiguration annotation

• Autoconfiguration classes are located in the org.springframework.boot.autoconfigure package

• Autoconfiguration classes are conditionally applied based on the presence of specific classes or properties
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Q2. Questions mostly on microservices and coding question on restTemplate
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Q1. Difference between hashmap and hash table
Ans. 
HashMap is non-synchronized and allows null values, while HashTable is synchronized and does not allow null values.
• HashMap is non-synchronized, meaning it is not thread-safe, while HashTable is synchronized and thread-safe.

• HashMap allows null values for both keys and values, while HashTable does not allow null keys or values.

• HashMap is generally preferred for non-thread-safe applications, while HashTable is used in mul
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Q2. Static block related questions
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Q3. Arraylist and linkedlist question
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