Bajaj Finserv android Application Development Software Engineer Interview Questions and Answers

Round duration - 60 Minutes
Round difficulty - Medium

This round had 1 very simple coding problem followed by some questions from Java and Spring.

Q1. 
Excel Column Number Conversion
Given a column title as it appears in an Excel sheet, your task is to return its corresponding column number.
Example:
Input:
S = "AB"
Output:
28
Explanation:
The seq...read more
Ans. 
Convert Excel column title to corresponding column number.
• Iterate through the characters in the input string from right to left

• Calculate the corresponding value of each character based on its position and multiply by 26^position

• Sum up all the values to get the final column number
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Q2. What is a lambda expression in Java, and how does it relate to a functional interface?
Ans. 
Lambda expression in Java is a concise way to represent a method implementation. It is related to functional interfaces by providing a single abstract method implementation.
• Lambda expressions allow you to write concise code by providing a way to represent a method implementation in a more compact form.

• Functional interfaces are interfaces with a single abstract method. Lambda expressions can be used to provide the imple...read more
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Q3. What are Java 8 streams?
Ans. 
Java 8 streams are a sequence of elements that support functional-style operations.
• Streams allow for processing collections of data in a declarative way.

• They support operations like filter, map, reduce, and collect.

• Streams can be sequential or parallel, allowing for efficient processing of large datasets.

• Example: List<String> names = Arrays.asList("Alice", "Bob", "Charlie"); Stream<String> stream = names.st
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Q4. What do you understand by autowiring in Spring Boot, and can you name the different modes of it?
Ans. 
Autowiring in Spring Boot is a feature that allows Spring to automatically inject dependencies into a Spring bean.
• Autowiring eliminates the need for explicit bean wiring in the Spring configuration file.

• There are different modes of autowiring in Spring Boot: 'byName', 'byType', 'constructor', 'autodetect', and 'no'.

• For example, in 'byName' mode, Spring looks for a bean with the same name as the property that needs to b
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Q5. What does the @SpringBootApplication annotation do internally?
Ans. 
The @SpringBootApplication annotation is used to mark the main class of a Spring Boot application.
• It is a combination of @Configuration, @EnableAutoConfiguration, and @ComponentScan annotations.

• It tells Spring Boot to start adding beans based on classpath settings, other beans, and various property settings.

• It is often placed on the main class that contains the main method to bootstrap the Spring Boot application.
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Q6. What are the basic annotations that Spring Boot offers?
Ans. 
Spring Boot offers basic annotations like @SpringBootApplication, @RestController, @Autowired, @RequestMapping, @Component, @Service, @Repository.
• @SpringBootApplication - Used to mark the main class of a Spring Boot application.

• @RestController - Used to define a RESTful controller.

• @Autowired - Used for automatic dependency injection.

• @RequestMapping - Used to map web requests to specific handler methods.

• @Component - Use...read more
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Round duration - 60 Minutes
Round difficulty - Medium

This round focused more on Multithreading concepts from Java and also some core concepts from OOPS.

Q1. What is a thread in Java?
Ans. 
A thread in Java is a lightweight sub-process that allows concurrent execution within a single process.
• Threads allow multiple tasks to be executed concurrently in a Java program.

• Each thread has its own stack and program counter, but share the same memory space.

• Threads can be created by extending the Thread class or implementing the Runnable interface.

• Example: Thread t1 = new Thread(new MyRunnable()); t1.start();
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Q2. What are the start() and run() methods of the Thread class in Java?
Ans. 
The start() method is used to start a new thread, while the run() method contains the code that will be executed by the thread.
• start() method is used to start a new thread and calls the run() method internally

• run() method contains the code that will be executed by the thread

• It is recommended to override the run() method with the desired functionality
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Q3. What is the difference between the Thread class and the Runnable interface when creating a thread in Java?
Ans. 
Thread class is a class in Java that extends the Thread class, while Runnable interface is an interface that implements the run() method.
• Thread class extends the Thread class, while Runnable interface implements the run() method.

• A class can only extend one class, so using Runnable interface allows for more flexibility in the class hierarchy.

• Using Runnable interface separates the task from the thread, promoting better d...read more
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Q4. What is the difference between an abstract class and an interface in OOP?
Ans. 
Abstract class can have both abstract and non-abstract methods, while interface can only have abstract methods.
• Abstract class can have constructor, fields, and methods, while interface cannot have any implementation.

• A class can only extend one abstract class, but can implement multiple interfaces.

• Abstract classes are used to define common behavior among subclasses, while interfaces are used to define a contract for cla...read more
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Q5. What is the garbage collector in Java?
Ans. 
Garbage collector in Java is a built-in mechanism that automatically manages memory by reclaiming unused objects.
• Garbage collector runs in the background to identify and delete objects that are no longer needed.

• It helps prevent memory leaks and optimize memory usage.

• Examples of garbage collectors in Java include Serial, Parallel, CMS, and G1.
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Q6. Can you explain the SOLID principles in Object-Oriented Design?
Ans. 
SOLID principles are a set of five design principles in object-oriented programming to make software designs more understandable, flexible, and maintainable.
• S - Single Responsibility Principle: A class should have only one reason to change.

• O - Open/Closed Principle: Software entities should be open for extension but closed for modification.

• L - Liskov Substitution Principle: Objects of a superclass should be replaceable...read more
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Round duration - 60 minutes
Round difficulty - Medium

This was a System Design Round where I was asked a LLD question to design a URL Shortener followed by a very standard question of LRU Cache. Overall this round went well and the interviewer was also quite satisfied by my answers.

Q1. Design a URL shortener.
Ans. 
A URL shortener service that generates short URLs for long links.
• Generate a unique short code for each long URL

• Store the mapping of short code to long URL in a database

• Redirect users from short URL to original long URL

• Implement analytics to track click-through rates
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Q2. 
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; otherw...read more
Ans. 
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 updates.

• When capacity is reached, evict the least recently used item before inserting a new item.

• Update the order of keys in the linked list whenever
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