Startup Java Developer Interview Questions and Answers

Q1. Quick sort - keep order same
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Q2. Reverse string with spaces but keep the space position intact
Ans. 
Reverse a string while keeping the position of spaces intact
• Split the string into an array of characters

• Iterate through the array and reverse the characters while keeping track of space positions

• Join the array back into a string
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Q1. Ask to write code for equal and hashcode in notepad
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Q2. Type of Collections and its internal working
Ans. 
Java collections are data structures that store and manipulate groups of objects.
• Types of collections include List, Set, Map, Queue, etc.

• Internal workings involve data structures like arrays, linked lists, hash tables, etc.

• Collections framework provides interfaces and classes for working with collections.
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Q3. Count number of occurrence of string from Array
Ans. 
Count occurrences of a specific string in an array of strings.
• Iterate through the array and use a HashMap to store the count of each string.

• Use the string as key and increment the count each time it is encountered.

• Return the count of the specific string at the end.
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Q4. Write a code using stream
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Using stream to filter a list of strings
• Use the filter method to apply a predicate to each element in the stream

• Convert the stream back to a list using the collect method
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Q1. Transactions in spring
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Transactions in Spring framework help manage database transactions in a consistent and reliable manner.
• Spring provides support for declarative transaction management using @Transactional annotation

• Transactions can be managed programmatically using TransactionTemplate

• Spring supports both programmatic and declarative transaction management

• Transactions ensure ACID properties (Atomicity, Consistency, Isolation, Durability)
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Q2. Static va virtual
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Q1. 1) How do you achieve concurrency in your current job, and write code for it? 2) Write code for Rest API using Springboot, need to write Entity, Service, Repository, and Controller classes? 3)Volatile keyw...read more
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Answers to common Java Developer interview questions
• 1) Concurrency is achieved using multithreading in Java. Use threads, executors, or synchronized blocks. Example: using ExecutorService to run multiple tasks concurrently.

• 2) Rest API in Springboot: Entity class defines database table, Service class contains business logic, Repository class interacts with database, Controller class handles HTTP requests.

• 3) Volatile key...read more
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Q1. Java 8 features, functional Interfaces and predefined functional interfaces, Streams
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Q2. Collections, Aggregations, solid principles in Java
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Q3. Design patterns, singleton and factory explain in detail
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Design patterns are reusable solutions to common problems in software design. Singleton ensures a class has only one instance, while factory creates objects without specifying the exact class.
• Design patterns are best practices for solving common software design problems.

• Singleton pattern ensures a class has only one instance and provides a global point of access to it.

• Factory pattern creates objects without specifying ...read more
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Q4. Spring functions, Spring Runners, Spring Exception handling
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Q5. Springboot annotations except common(any 5)
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Q6. Write spring boot program to accept json as request. write the logic and explain
Ans. 
Create a Spring Boot program to accept JSON requests and process the data.
• Create a Spring Boot application with a REST controller to handle incoming JSON requests.

• Use @PostMapping annotation to map the endpoint for accepting JSON requests.

• Use @RequestBody annotation to bind the incoming JSON data to a Java object.

• Process the JSON data as needed in the controller method.

• Return a response as JSON if required.
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3 coding questions were given and to be solved only in java

Simple java coding questions on file io, atomic integers etc

Round 1 was an online hackerank coding test + technical MCQs.

It consisted of 5 MCQs + 1 SQL problem + 1 DSA problem based on queue + 1 Graph question + 1 java based question to create a REST API.