Senior Java Developer
400+ Senior Java Developer Interview Questions and Answers

Asked in Oracle

Q. Remove the Kth Node from the End of a Linked List
You are given a singly Linked List with 'N' nodes containing integer data and an integer 'K'. Your task is to delete the Kth node from the end of this Linked Li...read more
Remove the Kth node from the end of a singly linked list.
Traverse the linked list to find the length 'N'.
Calculate the position to delete from the beginning as 'N - K + 1'.
Delete the node at the calculated position.
Handle edge cases like deleting the head or tail node.

Asked in Cisco

Q. Intersection of Linked List Problem
You are provided with two singly linked lists containing integers, where both lists converge at some node belonging to a third linked list.
Your task is to determine the data...read more
Find the node where two linked lists merge
Traverse both lists to find their lengths and the difference in lengths
Move the pointer of the longer list by the difference in lengths
Traverse both lists simultaneously until they meet at the merging node
Senior Java Developer Interview Questions and Answers for Freshers

Asked in Amazon

Q. Merge Two Sorted Linked Lists Problem Statement
You are provided with two sorted linked lists. Your task is to merge them into a single sorted linked list and return the head of the combined linked list.
Input:...read more
Merge two sorted linked lists into a single sorted linked list with linear time complexity and constant space usage.
Create a dummy node to start the merged list
Compare the values of the two linked lists and add the smaller value to the merged list
Move the pointer of the merged list and the pointer of the smaller value list forward
Continue this process until one of the lists is fully traversed
Append the remaining elements of the other list to the merged list
Return the head of ...read more

Asked in Amazon

Q. LRU Cache Design Question
Design a data structure for a Least Recently Used (LRU) cache that supports the following operations:
1. get(key)
- Return the value of the key if it exists in the cache; otherwise, re...read more
Design a Least Recently Used (LRU) cache data structure that supports get and put operations with capacity constraint.
Implement a doubly linked list to keep track of the order of keys based on their recent usage.
Use a hashmap to store key-value pairs for quick access and update.
When capacity is reached, evict the least recently used item before inserting a new item.
Asked in Caspex Corp

Q. How would you configure Jenkins or GitLab's CICD pipelines to trigger automatic builds, run unit tests, perform integration tests, deploy to artifactory, and produce a production environment using containerizat...
read moreSetting up CICD pipeline for Spring Boot microservices using Jenkins/GitLab
Configure Jenkins/GitLab to listen for changes in the repository
Set up build steps to compile the code, run unit tests, and perform integration tests
Use Docker for containerization and Kubernetes for container orchestration
Deploy artifacts to Artifactory and promote to production environment
Automate the entire process with appropriate triggers and notifications

Asked in Ernst & Young

Java is platform-independent because the code is compiled into bytecode which can run on any platform with a JVM, making the JVM platform-dependent.
Java code is compiled into bytecode, which is a platform-independent intermediate code
The JVM interprets and executes the bytecode on different platforms
The JVM acts as a layer of abstraction between the Java code and the underlying platform
The JVM is platform-dependent because it needs to be implemented specifically for each plat...read more
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Asked in Amdocs

The life cycle of a thread in Java involves creation, running, waiting, and termination.
A thread is created using the 'new' keyword or by implementing the Runnable interface.
The thread starts running when the start() method is called.
During execution, a thread can enter a waiting state using methods like sleep() or wait().
A thread terminates when its run() method completes or when the stop() method is called.

Asked in Sonata Software

Q. When should you use an abstract class versus an interface in Java?
Abstract classes are used for code reuse and interfaces are used for multiple inheritance and loose coupling.
Abstract classes can have both abstract and non-abstract methods while interfaces can only have abstract methods.
Abstract classes can have constructors while interfaces cannot.
Interfaces are used when a class needs to implement multiple behaviors while abstract classes are used for code reuse.
Interfaces promote loose coupling while abstract classes promote tight coupli...read more
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Asked in Amdocs

DELETE removes specific rows from a table, while TRUNCATE removes all rows and resets auto-increment values.
DELETE is a DML command, while TRUNCATE is a DDL command.
DELETE can be rolled back, while TRUNCATE cannot be rolled back.
DELETE triggers delete triggers, while TRUNCATE does not trigger them.
DELETE is slower as it logs individual row deletions, while TRUNCATE is faster as it logs the deallocation of the data pages.
Example: DELETE FROM table_name WHERE condition; TRUNCAT...read more
Asked in Caspex Corp

Q. Suppose your task is optimizing a Java application that handles a high volume of concurrent requests. How would you design the concurrency model, and what techniques would you employ to ensure thread safety and...
read moreDesigning a concurrency model for a high calling java application to ensure thread safety and maximize throughput while minimizing deadlock risks.
Use a combination of thread pools and executor services to manage concurrent requests efficiently.
Implement synchronization mechanisms such as locks, semaphores, or atomic variables to ensure thread safety.
Utilize non-blocking algorithms and data structures to reduce contention and avoid deadlocks.
Consider using asynchronous program...read more

Asked in Quest Global

Q. 1. What is runtime polymorphism? Can you explain by writing and example ? 2. Developer d = new Employee(); Here employee is a super class and Developer is a subclass. If we can d.work(); which method will be ex...
read moreThis response covers key Java concepts including runtime polymorphism, method overloading, array manipulation, and threading.
1. Runtime polymorphism occurs when a method call is resolved at runtime. Example: Method overriding in subclasses.
2. In 'Developer d = new Employee();', if d.work() is called, the 'work' method in Employee class will execute if overridden.
3. Yes, static methods can be overloaded by changing the parameter list. Example: 'static void method(int a) {}' an...read more
Asked in Caspex Corp

Q. Suppose the organization has a legacy system written in a different programming language integrated with your Java application. How would you approach the integration, considering factors such as data exchange...
read moreI would assess the legacy system's data exchange formats and communication protocols, then design a seamless integration plan.
Analyze the data exchange formats used by the legacy system and determine compatibility with Java application
Identify the communication protocols utilized by the legacy system and ensure they can be integrated with Java
Design a middleware layer or API to facilitate communication between the legacy system and Java application
Implement data mapping and t...read more
Asked in Caspex Corp

Q. Suppose your task is to design a highly available and scalable data storage solution for a mission-critical application. How would you choose between AWS and DynamoDB based on the application requirements?
Choose AWS for flexibility and customization, choose Dynamo DB for simplicity and scalability
Consider AWS if you need more flexibility and customization in your data storage solution
Choose Dynamo DB if you prioritize simplicity and scalability for your mission critical application
AWS offers a wide range of services and configurations for high availability and scalability, while Dynamo DB is a fully managed NoSQL database service that can automatically scale based on demand
If ...read more
Asked in Caspex Corp

Q. Suppose your microservice exposes an API that requires authentication and authorization to access specific data. How would you implement secure authentication and authorization using OAuth or JWT tokens? What m...
read moreImplement secure authentication and authorization using Auth or JWT token to prevent security vulnerabilities.
Use HTTPS to encrypt communication between client and server to prevent eavesdropping.
Implement strong password policies and use password hashing to securely store user credentials.
Use JWT tokens with short expiration times and refresh tokens to prevent token theft.
Implement role-based access control to ensure users only have access to authorized resources.
Regularly u...read more

Asked in Coforge

Q. What happens when you set the port number to 0 for a service in Spring Boot?
Setting port number as 0 in Spring Boot for a service
Setting port number as 0 allows the operating system to choose an available port
This is useful when running multiple instances of the same service on the same machine
To set port number as 0 in Spring Boot, add 'server.port=0' to application.properties or application.yml
Asked in Caspex Corp

Q. Your microservice interacts with an external API and database, resulting in frequent read and write operations. How would you optimize performance using caching techniques like Spring Cache Abstraction or distr...
read moreOptimize microservice performance with caching strategies like Spring Cache and distributed caching solutions.
Implement Spring Cache Abstraction to cache method results, reducing database calls.
Use annotations like @Cacheable, @CachePut, and @CacheEvict for fine-grained control over caching.
Consider distributed caching solutions like Redis or Hazelcast for scalability across multiple instances.
Cache external API responses to minimize latency and reduce the number of API calls...read more

Asked in Coforge

Q. What is the impact of changing annotations on Spring Boot classes?
Changing annotations on Spring Boot classes can have significant impact on the application.
Changing annotations can affect the behavior of the application
Annotations can control the lifecycle of beans, security, caching, etc.
Removing or modifying annotations can cause runtime errors
Adding new annotations can introduce new functionality
Annotations can affect the performance of the application

Asked in Capgemini

Q. 1.difference between list,set and map in java collections 2.exception Handling 3.difference between throw and throws 4.why to create a thread 5.maker interface in java and its use 6.Spring boot which you used i...
read moreInterview questions for Senior Java Developer
List is an ordered collection, Set is an unordered collection with no duplicates, Map is a key-value pair collection
Exception handling is used to handle runtime errors and prevent program crashes
Throw is used to throw an exception explicitly, Throws is used to declare an exception that a method may throw
Threads are used to execute multiple tasks simultaneously and improve program performance
Marker interface is an interface with no ...read more

Asked in Capgemini

Q. what is marker interface what is Stream api difference between Runnable and callable difference between comparable and compartor Internal working of hashMap Difference between Spring and Springboot
Marker interface is an interface with no methods, used to mark classes for special treatment.
Marker interface is an empty interface with no methods
It is used to mark classes for special treatment
Examples include Serializable, Cloneable interfaces
Asked in Caspex Corp

Q. Suppose you need to implement a reliable messaging system for communication between distributed components of your application. How could you design the messaging architecture using technologies like Kafka and...
read moreDesign a reliable messaging system using Kafka and RabbitMQ for communication between distributed components.
Use Kafka for high-throughput, low-latency messaging with strong durability guarantees.
Implement RabbitMQ for reliable message queuing and delivery.
Integrate Kafka for real-time event streaming and RabbitMQ for asynchronous communication.
Leverage Kafka Connect to easily connect Kafka with external systems and RabbitMQ plugins for enhanced functionality.

Asked in Quest Global

Q. 8. What is the difference between synchronized block and synchronised method ?? Which is better with respect to performance? 9. If we have static block, a constructer and main method. What is the order of execu...
read moreKey Java concepts including synchronization, execution order, design patterns, and SOLID principles.
Synchronized Block: Locks a specific block of code, allowing more granular control over synchronization.
Synchronized Method: Locks the entire method, which can lead to reduced concurrency.
Performance: Synchronized blocks are generally better for performance as they allow more flexibility.
Execution Order: Static blocks execute first, followed by the constructor, and then the mai...read more
Asked in Caspex Corp

Q. How would you implement service discovery and load balancing for microservices in a distributed environment using technologies like Netflix Eureka?
Implement service discovery and load balancing using Netflix Eureka for microservices communication.
Use Netflix Eureka as a service registry where microservices can register themselves and discover other services.
Each microservice will have a Eureka client that registers its instance with the Eureka server upon startup.
Eureka server provides a REST API for services to query for available instances of other services.
Load balancing can be achieved using Ribbon, which integrates...read more
Asked in Caspex Corp

Q. Your team is migrating a monolithic application to a microservices application deployed on AWS ECS. How would you design the containerized application using Docker and orchestrate the deployment with ECS?
Designing a microservices architecture on AWS ECS involves containerization, service decomposition, and orchestration strategies.
Identify and decompose the monolithic application into microservices based on business capabilities.
Create Docker images for each microservice, ensuring they are lightweight and include only necessary dependencies.
Use Docker Compose for local development to manage multi-container applications easily.
Define ECS task definitions for each microservice,...read more

Asked in Citicorp

Q. What are the Java 8 Features you've worked with?
Java 8 introduced several new features including lambda expressions, functional interfaces, and streams.
Lambda expressions allow for more concise and functional programming style.
Functional interfaces enable the use of lambda expressions.
Streams provide a powerful way to process collections of data in a functional manner.
Default methods in interfaces allow for adding new methods to existing interfaces without breaking compatibility.
Optional class helps to handle null values m...read more

Asked in HCLTech

Q. 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?
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.

Asked in Cognizant

Q. 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?
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())
Asked in Smartavya Analytica

Q. What is the difference between the different versions of java (8, 11, 17). Tell about the new features you have worked on?
Java versions 8, 11, and 17 have introduced various new features and improvements.
Java 8 introduced lambda expressions, streams, and the new Date and Time API.
Java 11 introduced local-variable syntax for lambda parameters, HTTP client API, and Flight Recorder.
Java 17 introduced sealed classes, pattern matching for switch statements, and enhanced foreign function and memory API.

Asked in Coforge

Q. Write a program to filter employees using Java streams.
Program to filter employees using Java streams
Create a list of employees
Use stream() method to convert list to stream
Use filter() method to filter employees based on condition
Use collect() method to convert stream back to list

Asked in Xtranet Technologies

Q. What is immutability, and how can we create our own immutable class?
Immutable objects are those whose state cannot be changed after creation.
Use final keyword to make class immutable
Make all fields private and final
Do not provide setter methods
If a field is mutable, return a copy of it instead of the original object
Examples: String, Integer, LocalDate
Asked in Caspex Corp

Q. Describe how you would implement the circuit breaker pattern using Spring Boot to handle failures and cascading failures in a distributed microservice environment when dealing with external service dependencies...
read moreImplementing circuit breaker pattern in Spring Boot to handle failures in a distributed environment
Use Spring Boot's resilience4j library to implement the circuit breaker pattern
Configure the circuit breaker to monitor the external service dependency and trip open when failures exceed a certain threshold
Handle the circuit breaker state transitions (OPEN, HALF_OPEN, CLOSED) appropriately in your code
Implement fallback mechanisms to gracefully handle failures when the circuit b...read more
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