Wissen Technology Java Software Developer Interview Questions and Answers

Q1. Given an array of non-negative integers.Find the length of the longest subsequence such that elements in the subsequence are contiguous integers. The consecutive numbers can be in any order. Example n=7 nu...read more
Ans. 
Find the length of the longest subsequence of contiguous integers in an array.
• Sort the array

• Iterate through the array and check for consecutive integers

• Keep track of the longest subsequence found
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Q2. Get list of pincodes from these objects Employee{ id Long, name String, Addresses : List
} Addresses{ houseNo long, pindcode long, state String, country String, } Ans. Use flatMap to flatten and then use m...read more
Ans. 
Use flatMap and map to extract list of pincodes from Employee objects
• Use flatMap to flatten the list of Addresses in each Employee object

• Use map to iterate over the flattened list and extract the pincodes

• Example: employeeList.stream().flatMap(emp -> emp.getAddresses().stream()).map(address -> address.getPincode()).collect(Collectors.toList())
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Q3. What is Database Pooling, Hikari and its configurations. Java 8 to current enchancements and current java version Factory and Builder design patterns to explain and code Project expalantion and details, Cr...read more
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Database pooling is a technique used to manage a pool of database connections for efficient resource utilization. HikariCP is a popular database connection pooling library in Java.
• HikariCP is a high-performance database connection pooling library for Java applications.

• It is known for its low latency and high throughput.

• Configurations for HikariCP include settings such as maximum pool size, connection timeout, and idle ...read more
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Q1. Explain Spring Boot
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Q2. What is Redux in React
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Q3. What is Context API in React
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It was medium level java coding questions along with springboot, mcqs

Q1. ArrayList vs LinkedList
Ans. 
ArrayList is better for random access and LinkedList is better for frequent insertions and deletions.
• ArrayList uses dynamic array to store elements, allowing fast random access but slower insertions and deletions.

• LinkedList uses doubly linked list to store elements, allowing fast insertions and deletions but slower random access.

• Example: Use ArrayList when you need to frequently access elements by index. Use LinkedList...read more
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Q2. HashMap working
Ans. 
HashMap is a data structure in Java that stores key-value pairs and allows fast retrieval of values based on keys.
• HashMap is part of the Java Collections framework.

• It allows null keys and values.

• HashMap does not maintain insertion order.

• Example: HashMap map = new HashMap<>();
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Coding round is related to DSA

Q1. Java related questions
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Q2. Explain about your project
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Q1. Salary negotiation
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Q2. Why you want to join us?
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Technology advantage or not

All aptitude topics,logical reasoning

Q1. Oops,2 coding questions
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Q2. Palindrome,even number
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Q1. What do you know
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Q2. Do you have any questions
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Q1. Basic questions on Java concepts like OOPS, multi threading, stream. MySQL join queries
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Q2. Questions on Spring Boot and REST API
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Q1. Questions on currently working project?.
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Q2. Your contribution to the project and what challenges you faced?
Ans. 
I contributed by developing new features and fixing bugs. Faced challenges with integrating third-party APIs.
• Developed new features such as user authentication and data visualization

• Fixed bugs related to database queries and UI responsiveness

• Challenges faced with integrating third-party APIs like payment gateways and social media platforms
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Q1. REST API for User CRUD
Ans. 
Design a RESTful API for CRUD operations on user resources.
• Use HTTP methods like GET, POST, PUT, DELETE for CRUD operations

• Create endpoints like /users for listing all users, /users/{id} for specific user

• Use status codes like 200 for success, 404 for not found, 400 for bad request

• Implement authentication and authorization mechanisms for security

• Include request and response body formats like JSON or XML
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Q2. Two Sum Leetcode problem
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Q3. Basic questions based on the candidate technical skills
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Q1. Basics to Intermediate level of questions based on the skills mentioned in the resume
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Q2. Projects related discussions
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Q1. I was informed to upload the supporting documents. ( They rejected me after this eventhough all my documents are genuine )
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