Subex Software Engineer Trainee Interview Questions and Answers

Q1. Difference between static and final
Ans. 
Static is used to define class-level variables and methods, while final is used to define constants that cannot be changed.
• Static variables belong to the class itself, while final variables are constants that cannot be modified.

• Static methods can be called without creating an instance of the class, while final methods cannot be overridden.

• Static variables are shared among all instances of a class, while final variables...read more
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Q2. ArraysList vs LinkedList
Ans. 
ArrayList is better for random access, LinkedList is better for frequent insertions/deletions.
• ArrayList uses dynamic array to store elements, LinkedList uses doubly linked list.

• ArrayList provides fast random access to elements using index, LinkedList provides fast insertion/deletion at any position.

• Example: ArrayList is suitable for scenarios where random access is required like searching, LinkedList is suitable for sc...read more
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Q3. Describe Java8 Features
Ans. 
Java8 introduced several new features including lambda expressions, functional interfaces, streams, and default methods.
• Lambda expressions allow you to write code in a more concise and readable way.

• Functional interfaces are interfaces with a single abstract method, which can be implemented using lambda expressions.

• Streams provide a way to work with collections of objects in a functional style.

• Default methods allow inte...read more
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Q4. Gave one scenario to solve using streams in java8
Ans. 
Using streams in Java 8 to filter and map a list of numbers
• Create a list of numbers

• Use stream to filter out even numbers

• Use map to square each number

• Collect the results into a new list
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Q5. Multithreading- Write program to print even and odd numbers from 1 to 20 using 2 threads. 1 thread will responsible for printing even and another for Odd. And print in such a manner it should be alternate....read more
Ans. 
Program to print even and odd numbers from 1 to 20 using 2 threads alternately.
• Create two threads, one for printing even numbers and one for printing odd numbers.

• Use wait(), notify(), and notifyAll() to ensure alternate printing.

• Ensure synchronization between the two threads to avoid race conditions.

• Example: Thread 1 prints even numbers (2, 4, 6, ...) and Thread 2 prints odd numbers (1, 3, 5, ...).
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Q6. Why strings immutable
Ans. 
Strings are immutable to ensure data integrity and security.
• Immutable strings prevent accidental changes to data

• Immutable strings allow for safe sharing of data between different parts of a program

• Immutable strings help prevent security vulnerabilities like SQL injection attacks
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Q7. Outer Join SQL query
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Q8. What is the purpose of using default methods in java8?
Ans. 
Default methods in Java 8 allow interfaces to have method implementations, enabling backward compatibility and reducing code duplication.
• Default methods were introduced in Java 8 to provide a way to add new methods to interfaces without breaking existing implementations.

• They allow interfaces to have method implementations, which was not possible before Java 8.

• Default methods can be overridden in implementing classes to...read more
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Q1. 1 coding problem related to Anagrams
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Q2. 1 Java8 streams problem
Ans. 
Using Java8 streams to solve a problem
• Use stream() method to convert a collection into a stream

• Use filter() method to filter elements based on a condition

• Use map() method to transform elements

• Use collect() method to collect the elements into a new collection
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Q3. What are checked exceptions
Ans. 
Checked exceptions are exceptions that must be either caught or declared in the method signature.
• Checked exceptions are subclasses of Exception (excluding RuntimeException and its subclasses)

• Checked exceptions must be either caught using try-catch block or declared in the method signature using 'throws' keyword

• Examples of checked exceptions in Java include IOException, SQLException, and ClassNotFoundException
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Q4. Purpose of @SpringBootApplication annotation?
Ans. 
Annotation used to mark a class as a Spring Boot application
• Combines @Configuration, @EnableAutoConfiguration, and @ComponentScan annotations

• Used to bootstrap and launch a Spring application

• Automatically scans for Spring components in the package and sub-packages
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Q5. Use of @Qualifier
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Annotation used in Spring to specify which bean to autowire
• Used to disambiguate when multiple beans of the same type are present

• Can be used with @Autowired to specify which bean to inject

• Helps in resolving dependencies when multiple beans of the same type are available
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Q6. What are microservices?
Ans. 
Microservices are a software development technique where an application is composed of small, independent services that communicate with each other.
• Microservices are designed to be small, focused on specific tasks, and independently deployable.

• Each microservice typically runs its own process and communicates with other services through APIs.

• Microservices allow for easier scalability, flexibility, and maintenance compar...read more
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Q7. Design patterns
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Q8. How microservices communicate with each other
Ans. 
Microservices communicate with each other through APIs, messaging queues, or service meshes.
• APIs: Microservices can communicate with each other by exposing APIs that allow them to send and receive data.

• Messaging queues: Microservices can use messaging queues like RabbitMQ or Kafka to send messages to each other asynchronously.

• Service meshes: Microservices can communicate through a service mesh like Istio, which handles...read more
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Q1. Asked about projects.
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Q2. Complete flow and business use case of the project
Ans. 
The project involves creating a web-based platform for online shopping with features like user registration, product browsing, shopping cart, and payment processing.
• User registers on the platform with personal information

• User browses products by category or search

• User adds products to the shopping cart

• User proceeds to checkout and makes payment

• Order is confirmed and user receives a confirmation email
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Q3. Interviewer was more concerned about matching the tech stack with job description
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2-3 basic dsa questions

Q1. Basic dsaquestions basic dsa
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Q2. Basic dsa questions basic dsa
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