Virinchi Technologies Junior Java Developer Interview Questions and Answers

Aptitude test like technical questions

Coding test for technical analysis

Q1. HR is asking same basic questions java
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Q1. Technical questions asked
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Q2. Full stack java developer
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Q1. Implement a custom stack that allows fetching the minimum element in constant time, O(1).
Ans. 
Custom stack with constant time access to minimum element
• Use two stacks - one to store elements and another to store minimum values

• When pushing an element, compare with top of min stack and push the smaller value

• When popping an element, pop from both stacks

• Access minimum element in O(1) time by peeking at top of min stack
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Q2. How can one create an immutable class named Employee with fields for name and hobbies defined as List?
Ans. 
To create an immutable class named Employee with fields for name and hobbies defined as List<String>, use private final fields and return new instances in getters.
• Use private final fields for name and hobbies in the Employee class

• Provide a constructor to initialize the fields

• Return new instances or unmodifiable lists in the getters to ensure immutability
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Q3. What changes are required in the Employee class to use it as a key for a HashMap?
Ans. 
Add hashCode() and equals() methods to Employee class.
• Override hashCode() method to generate a unique hash code for each Employee object.

• Override equals() method to compare Employee objects based on their attributes.

• Ensure that the attributes used in hashCode() and equals() methods are immutable.

• Example: Add id, name, and department attributes to Employee class and override hashCode() and equals() methods based on thes
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Q4. What is the implementation of the singleton design pattern?
Ans. 
Singleton design pattern ensures a class has only one instance and provides a global point of access to it.
• Create a private static instance of the class within the class itself.

• Provide a public static method to access the instance, creating it if necessary.

• Ensure the constructor of the class is private to prevent instantiation from outside the class.

• Use lazy initialization to create the instance only when needed.

• Thread...read more
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Q5. Different ways to create a thread
Ans. 
Ways to create a thread in Java include extending the Thread class, implementing the Runnable interface, and using Java 8's lambda expressions.
• Extend the Thread class and override the run() method

• Implement the Runnable interface and pass it to a Thread object

• Use Java 8's lambda expressions with the Executor framework
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Q6. What are the SOLID principles in software design, and can you provide examples for each?
Ans. 
SOLID principles are a set of five design principles in object-oriented programming to make software more maintainable, flexible, and scalable.
• Single Responsibility Principle (SRP) - A class should have only one reason to change. Example: A class that handles user authentication should not also handle database operations.

• Open/Closed Principle (OCP) - Software entities should be open for extension but closed for modific...read more
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Q1. What is the concept of Object-Oriented Programming (OOP) and can you provide an example?
Ans. 
OOP is a programming paradigm based on the concept of objects, which can contain data in the form of fields and code in the form of procedures.
• OOP focuses on creating objects that interact with each other to solve a problem.

• Encapsulation is a key concept in OOP, where data is kept within an object and only accessible through its methods.

• Inheritance allows objects to inherit attributes and methods from parent classes.

• Po...read more
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Q2. How do threads communicate with each other in Java?
Ans. 
Threads communicate in Java through shared memory or message passing.
• Threads can communicate through shared variables in memory.

• Threads can communicate through synchronized methods or blocks.

• Threads can communicate through wait(), notify(), and notifyAll() methods.

• Threads can communicate through message passing using classes like BlockingQueue or ExecutorService.
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Q3. Write a program to reverse a linked list.
Ans. 
Program to reverse a linked list
• Create a new linked list to store the reversed elements

• Traverse the original linked list and insert each node at the beginning of the new list

• Update the head of the new list as the last node of the original list
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Q4. What is the difference between string literals and the string pool?
Ans. 
String literals are constant strings defined in code, while the string pool is a memory area where unique string objects are stored.
• String literals are created using double quotes, while string pool objects are created using the 'new' keyword.

• String literals are stored in the string pool to conserve memory and improve performance.

• String literals are automatically interned by the JVM, while string pool objects need to b
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Q5. What is the program to print the 90-degree rotated view of a 2D array?
Ans. 
Program to print the 90-degree rotated view of a 2D array.
• Iterate through each column in reverse order and print the corresponding row elements.

• Repeat this process for all columns to get the rotated view of the 2D array.
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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
Ans. 
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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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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Q1. Difference between Hashset and Treeset
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Q2. Final Finally and finalize difference
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1 Assignment which you need to solve in front of the interviewer

Q1. Questions on Java Streams
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Q2. Questions on springboot
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Q1. Basic java and API
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Q1. Normal Question
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