Protechsoft Technologies Java Programmer Interview Questions and Answers

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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Q1. What are primitive and non primitive data types
Ans. 
Primitive data types are basic data types provided by the programming language, while non-primitive data types are created by the programmer.
• Primitive data types include int, float, double, char, boolean, etc.

• Non-primitive data types include arrays, classes, interfaces, etc.

• Primitive data types store actual values, while non-primitive data types store references to objects.
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Q2. What are access modifiers and non access modifiers
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Access modifiers control the visibility of classes, methods, and variables. Non-access modifiers provide additional functionality.
• Access modifiers: public, private, protected, default

• Non-access modifiers: static, final, abstract, synchronized

• Example: public class MyClass { private int myVar; }
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Q3. What are all Java 8 features and explain the one which we have used in our project
Ans. 
Java 8 features include lambda expressions, functional interfaces, streams, and more.
• Lambda expressions allow concise syntax for defining anonymous functions.

• Functional interfaces can have only one abstract method and are used for lambda expressions.

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

• Optional class helps to avoid NullPointerException by wrapping a value that may be null.
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Q4. CICD tools which we have used explain in high level
Ans. 
CICD tools automate the process of building, testing, and deploying code changes.
• Popular CICD tools include Jenkins, GitLab CI/CD, CircleCI, and Travis CI

• These tools help in automating the software development lifecycle

• They enable continuous integration, continuous delivery, and continuous deployment

• CICD tools help in improving code quality, reducing manual errors, and increasing development speed
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Q5. What is containerization
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Containerization is a lightweight, portable, and self-sufficient way to package and run applications.
• Containerization involves encapsulating an application and its dependencies into a container image.

• Containers are isolated from each other and share the host OS kernel.

• Popular containerization platforms include Docker and Kubernetes.

• Containerization allows for easy deployment and scaling of applications.
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Q6. What is indexing in sql
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Indexing in SQL is a technique used to improve the performance of queries by creating a data structure that allows for faster retrieval of data.
• Indexes are created on columns in a database table to speed up the retrieval of rows that match a certain condition in a query.

• They work similar to the index in a book, allowing the database to quickly locate the rows that satisfy the query.

• Indexes can be created using a single...read more
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Q7. Programming question on stream like finding the longest string in a given list of string
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Q1. They asked some core Java Concepts,String,Java 8,SpringBoot Architecture,Stream API code
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Aptitude questions and some questions from PostgreSQL.

Q1. Java fundamental questions?
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Q2. Collection Framework.
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Q3. 2-3 easy to medium Coding Questions.
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Q4. Questions from Object oriented programming in Java?
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Q5. Implementation of HashMap , LinkedList, HashSet, Heap?
Ans. 
HashMap, LinkedList, HashSet, and Heap are data structures commonly used in Java for storing and organizing data.
• HashMap: key-value pairs, uses hashing to store and retrieve elements efficiently (e.g. HashMap)

• LinkedList: linear data structure, elements are stored in nodes with pointers to the next node (e.g. LinkedList)

• HashSet: collection of unique elements, uses hashing to ensure uniqueness (e.g. Hash...read more
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Q1. Ooops questions asked for me
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Q2. Collections questions asked for me
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Q1. Normal questions
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Q1. Comparable vs Comparator
Ans. 
Comparable is an interface used for natural ordering, while Comparator is used for custom ordering in Java.
• Comparable interface is used to define the natural ordering of objects. It is implemented by the class whose objects are to be sorted.

• Comparator interface is used to define custom ordering of objects. It is implemented by a separate class that compares objects based on specific criteria.

• Example: Sorting a list of ...read more
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Q2. Difference between List and Set

Ans. 

List allows duplicate elements and maintains insertion order, while Set does not allow duplicates and does not maintain order.

• List can contain duplicate elements, Set cannot

• List maintains insertion order, Set does not guarantee order

• List is implemented by classes like ArrayList, LinkedList, Set is implemented by classes like HashSet, TreeSet

• Example: List list = new ArrayList<>(); Set set = new HashSet<>();

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