UST Lead Java Developer Interview Questions and Answers

Q1. Explain architecture of your project
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Q2. Some questions on Java, Spring Boot and sql
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Q1. Project flow and some behavioural questions
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Q2. Project contribution of yours
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Developed a web application for tracking employee attendance and performance
• Implemented user authentication and authorization using Spring Security

• Utilized Hibernate for database interaction and data persistence

• Designed and developed RESTful APIs for frontend integration

• Used AngularJS for frontend development to create interactive user interfaces
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Q1. Basic formalities before offer release
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Q1. What are primitive and non primitive data types
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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
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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
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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. Basics of java like string ,string builder ,Buffer,scp
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Q2. Spring boot annotaions
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Q1. Explain how hashmap internally works
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HashMap internally uses an array of linked lists to store key-value pairs.
• HashMap uses hashing to determine the index of the key in the array.

• If multiple keys hash to the same index, a linked list is used to store them.

• When retrieving a value, the key is hashed to find the index and then the linked list is searched for the key.
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Q2. Difference between vector and Arraylist
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Vector is synchronized and slower, ArrayList is unsynchronized and faster.
• Vector is synchronized, ArrayList is not.

• Vector is slower due to synchronization, ArrayList is faster.

• Vector is legacy class, ArrayList is part of Java Collections framework.

• Vector doubles its size when full, ArrayList increases by 50%.
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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. Java 8 features
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Q2. Collections , and internal working hashmap
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They asked question about myself

Gave codeing in advance java concepts

1. Find longest repeating character from back.
2. Find all non-duplicates in an array and return in sorted manner.

Q1. Suppose we have more 2 interfaces with the same default method. What will happen when we try to implment both the interfaces in the same class.?
Ans. 
The class will have to provide its own implementation of the conflicting default method.
• When implementing multiple interfaces with the same default method, a class must provide its own implementation of the conflicting method.

• The class cannot inherit the default implementation from both interfaces.

• The class can choose to implement one of the default methods and provide its own implementation for the other.

• Alternatively...read more
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Q2. Terminal vs Intermediate Operations in streams
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Terminal operations in streams produce a result or a side effect, while intermediate operations transform or filter the data.
• Terminal operations are the final operations in a stream pipeline, such as forEach, collect, or reduce.

• Intermediate operations are operations that can be chained together, such as filter, map, or sorted.

• Terminal operations trigger the processing of the stream and produce a result or a side effect...read more
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Q3. Try vs try-with-resources
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try vs try-with-resources
• The 'try' statement is used to define a block of code to be tested for exceptions.

• The 'try-with-resources' statement is used to automatically close resources that implement the AutoCloseable interface.

• Try-with-resources is more concise and less error-prone compared to try-catch-finally.

• Try-with-resources can handle multiple resources in a single statement.
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Q4. Iterator vs ListIterator
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Iterator is a universal interface for iterating over a collection, while ListIterator is a specialized interface for iterating over lists.
• Iterator can only move forward, while ListIterator can move in both directions.

• ListIterator has additional methods like previous(), hasPrevious(), and add().

• ListIterator is only available for List implementations, while Iterator can be used with any collection.
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Q5. What are projections in Spring Data JPA?
Ans. 
Projections in Spring Data JPA allow customizing the shape of the data returned from a query.
• Projections are used to retrieve specific fields or a subset of fields from an entity.

• They help in reducing the amount of data transferred over the network.

• Projections can be defined using interfaces or classes.

• They can be used with both JPQL and native SQL queries.

• Projections can be used to fetch related entities as well.
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Q6. What are the two types of compiler in angular?
Ans. 
The two types of compiler in Angular are JIT (Just-in-Time) compiler and AOT (Ahead-of-Time) compiler.
• JIT compiler compiles the code at runtime in the browser.

• AOT compiler compiles the code before the application is deployed to the browser.

• JIT compilation is slower but allows for faster development and debugging.

• AOT compilation is faster but requires additional build step before deployment.
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Q7. What are the different types of data binding in Angular?
Ans. 
Data binding in Angular allows automatic synchronization of data between the model and the view.
• Interpolation: {{ }} - binds data from the component to the view

• Property binding: [] - binds data from the component to an element property

• Event binding: () - binds an event from the view to a method in the component

• Two-way binding: [()] - combines property and event binding to achieve two-way data flow
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Q8. Promises vs Observables
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Promises are used for asynchronous programming in JavaScript, while Observables are used for reactive programming.
• Promises represent a single value that may be available now or in the future.

• Observables represent a stream of values that can be emitted over time.

• Promises are eager, meaning they start executing as soon as they are created.

• Observables are lazy, meaning they only start executing when subscribed to.

• Promises...read more
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Q9. Constructor vs ngOnInit
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Constructor is a special method used to initialize an object, while ngOnInit is a lifecycle hook in Angular.
• Constructor is used to create and initialize an object of a class.

• ngOnInit is a lifecycle hook in Angular that is called after the component is initialized.

• Constructor is defined using the constructor keyword, while ngOnInit is a method defined in the component class.

• Constructor is called only once during the cre...read more
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Q10. When to use Inline Template vs External Template in Angular?
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Inline templates are used for small, simple templates, while external templates are used for larger, complex templates.
• Inline templates are defined within the component's TypeScript file using the template property.

• External templates are defined in separate HTML files and linked to the component using the templateUrl property.

• Inline templates are useful for small components or when the template is simple and doesn't re...read more
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Q11. Which module is used for http calls in Angular?
Ans. 
HttpClient module is used for http calls in Angular.
• HttpClient module is part of the @angular/common/http package.

• It provides a simplified API for making HTTP requests.

• It supports various HTTP methods like GET, POST, PUT, DELETE, etc.

• It also supports features like request/response headers, query parameters, error handling, etc.

• Example: import { HttpClient } from '@angular/common/http';
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