Limestone Java Developer Interview Questions and Answers

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 ?
Ans. 
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?
Ans. 
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
Ans. 
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. 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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Q1. What are virtual threads and its uses
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Q2. Differenciate deep cloning vs shallow cloning with a code
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Onlin test consist pf easy numerical questions

Easy questions not so difficult

Q1. Java oops concept
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Q2. Basic sprophramming questions
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Q3. Networking firewall cisco
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Q1. Personal questions
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Q2. Whetehr to willing to work in any locations
Ans. 
Yes, I am willing to work in any location for the right opportunity.
• I am open to relocating for the right job opportunity

• I am flexible and adaptable to new environments

• I believe working in different locations can provide valuable experiences and growth opportunities
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First round is quit easy

2 coding question based on dsa

Q1. Explain different phases of sdlc
Ans. 
SDLC stands for Software Development Life Cycle, which consists of different phases from planning to maintenance.
• 1. Planning phase involves defining project scope, requirements, and creating a project plan.

• 2. Analysis phase focuses on gathering and analyzing requirements to create a detailed system design.

• 3. Design phase involves creating a high-level design, detailed design, and architecture for the software.

• 4. Implem...read more
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Q2. 4 paillers of datastructure.
Ans. 
The 4 pillars of data structure are arrays, linked lists, stacks, and queues.
• Arrays: Data structure that stores a collection of elements with a fixed size.

• Linked Lists: Data structure where each element points to the next element in the sequence.

• Stacks: Data structure that follows the Last In First Out (LIFO) principle.

• Queues: Data structure that follows the First In First Out (FIFO) principle.
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