20+ Edunext Technologies Interview Questions and Answers

Abstract class can have both abstract and non-abstract methods, while interface can only have abstract methods.

• Abstract class can have constructors, fields, and methods, while interface cannot have any implementation.

• A class can implement multiple interfaces but can only inherit from one abstract class.

• Abstract classes are used to define a common base class for related classes, while interfaces are used to define a contract for classes to implement.

• Example: Abstract class 'Sh...read more

MVC architecture consists of three components - Model, View, and Controller, each with its own responsibilities.

• Model represents the data and business logic of the application.

• View is responsible for displaying the data to the user.

• Controller acts as an intermediary between Model and View, handling user input and updating the Model accordingly.

• Changes in one component do not directly affect the others, promoting separation of concerns.

• Example: In a web application, the Model ...read more

Intermediate operations return a new stream and allow further operations, while terminal operations produce a result or side-effect.

• Intermediate operations include filter(), map(), sorted(), etc.

• Terminal operations include forEach(), collect(), reduce(), etc.

• Intermediate operations are lazy and only executed when a terminal operation is called.

• Terminal operations are eager and trigger the stream to process the data.

A hash map in Java is a data structure that stores key-value pairs and uses hashing to efficiently retrieve values based on keys.

• Hash map uses an array to store key-value pairs.

• Keys are hashed to determine the index where the value will be stored.

• Collision resolution techniques like chaining or open addressing are used to handle hash collisions.

• Example: HashMap<String, Integer> map = new HashMap<>(); map.put("key", 123); int value = map.get("key");

MVC architecture separates concerns, improves code organization, promotes reusability, and enhances maintainability.

• Separates concerns: MVC separates the application into three main components - Model, View, and Controller, allowing for easier management of code and logic.

• Improves code organization: Each component in MVC has a specific role, making it easier to organize and maintain code.

• Promotes reusability: With clear separation of concerns, components can be reused in diff...read more

RANK() assigns a unique rank to each row based on the specified column, while ROW_NUMBER() assigns a unique sequential row number to each row.

• RANK() may have gaps in the ranking if there are ties, while ROW_NUMBER() will not have any gaps.

• RANK() will assign the same rank to rows with the same value, while ROW_NUMBER() will assign a unique row number to each row.

• ROW_NUMBER() is used to generate a unique sequential number for each row in a result set, while RANK() is used to as...read more

StringBuffer is synchronized and thread-safe, while StringBuilder is not synchronized and faster.

• StringBuffer is synchronized, making it thread-safe for use in multi-threaded environments.

• StringBuilder is not synchronized, making it faster but not thread-safe.

• Use StringBuffer when thread safety is needed, and StringBuilder for better performance in single-threaded scenarios.

Override and virtual are keywords in C# used for method overriding and polymorphism.

• Override keyword is used to provide a new implementation for a method in a derived class that is already defined in a base class.

• Virtual keyword is used to allow a method to be overridden in a derived class.

• Override keyword is used in the derived class to indicate that a method overrides a base class method.

• Virtual keyword is used in the base class to indicate that a method can be overridden i...read more

CTE is a temporary result set that can be referenced within a SELECT, INSERT, UPDATE, or DELETE statement in SQL.

• CTEs help improve readability and maintainability of complex SQL queries.

• They can be recursive, allowing for hierarchical data querying.

• CTEs are defined using the WITH keyword followed by the CTE name and query.

• Example: WITH cte_name AS (SELECT * FROM table_name) SELECT * FROM cte_name;

Memory for a string in Java is allocated on the heap, with a reference stored on the stack.

• Strings in Java are immutable, so once created they cannot be changed.

• String objects are stored on the heap, while references to them are stored on the stack.

• String literals are stored in a special memory area called the String Pool.

• String objects can also be created using the 'new' keyword.

Types of hashmaps in Java include HashMap, LinkedHashMap, and TreeMap.

• HashMap: basic implementation, no order guaranteed

• LinkedHashMap: maintains insertion order

• TreeMap: sorted by natural order or custom comparator

Java 8 introduced several new features including lambda expressions, functional interfaces, streams, and the new Date and Time API.

• Lambda expressions allow you to write more concise code by providing a way to pass functions as arguments.

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

• Streams provide a way to work with sequences of elements and perform aggregate operations on them.

• The new Date and Time API p...read more

HashMap is non-synchronized and allows null values and keys, while HashTable is synchronized and does not allow null values or keys.

• HashMap is non-synchronized, meaning it is not thread-safe, while HashTable is synchronized and thread-safe.

• HashMap allows null values and keys, while HashTable does not allow null values or keys.

• HashMap is generally preferred for non-threaded applications, while HashTable is used in multi-threaded environments.

• Example: HashMap map = new HashMap<...read more

Web APIs are used to allow different software applications to communicate with each other over the internet.

• Web APIs allow different systems to interact and share data

• They enable developers to access specific features or data from a remote server

• They help in building more dynamic and interactive web applications

• Examples include Google Maps API for integrating maps into websites, Twitter API for accessing tweets, and Spotify API for music streaming

A stored procedure is a set of SQL statements that are stored in the database and can be called by name to perform a specific task.

• Stored procedures can improve performance by reducing network traffic and improving security.

• They can be reused across multiple applications and users.

• Stored procedures can accept input parameters and return output parameters or result sets.

• Example: CREATE PROCEDURE GetEmployeeDetails AS SELECT * FROM Employees WHERE Department = 'IT';

Dependency injection is a design pattern where components are given their dependencies rather than creating them internally.

• Allows for easier testing by providing mock dependencies

• Promotes loose coupling between components

• Improves code reusability and maintainability

• Examples: Constructor injection, Setter injection, Interface injection

Controller method for validating user name and password

• Accept user input for username and password

• Check if username and password meet specified criteria (e.g. length, special characters)

• Query database to verify if username and password match stored credentials

• Return success or error message based on validation results

Streams in software development are sequences of data that can be processed sequentially or in parallel.

• Streams are used for processing large amounts of data efficiently.

• They can be used for reading from or writing to files, network connections, or other sources.

• Streams can be processed synchronously or asynchronously.

• Examples include reading a file line by line, processing a stream of sensor data, or downloading a large file in chunks.

Use Java 8 stream API to sort a list of integers

• Use stream() method to convert the list to a stream

• Use sorted() method to sort the integers

• Collect the sorted integers back to a list using collect() method

Java 8 stream is a sequence of elements that supports functional-style operations.

• Java 8 stream allows for processing collections of objects in a functional way.

• Streams can be created from various data sources like collections, arrays, or I/O resources.

• Common stream operations include map, filter, reduce, and collect.

• Streams are lazy, meaning they only perform operations when necessary.

• Example: List names = Arrays.asList("Alice", "Bob", "Charlie"); Stream stream = names.strea...read more

A clonable object is an object that can create a copy of itself, allowing for duplication without affecting the original object.

• Clonable objects implement the Cloneable interface in Java.

• The clone() method is used to create a copy of the object.

• Cloning can be shallow or deep, depending on the requirements.

• Examples of clonable objects include ArrayList, HashMap, and custom classes that implement Cloneable.

ODATA Service is a protocol for querying and updating data using RESTful APIs.

• ODATA stands for Open Data Protocol

• It allows for querying and updating data using standard HTTP methods

• Supports filtering, sorting, and pagination of data

• Commonly used in web and mobile applications for data access

Java 8 introduced lambda expressions, functional interfaces, streams, and default methods in interfaces.

• Lambda expressions allow you to pass functionality as an argument to a method.

• Functional interfaces have a single abstract method and can be used with lambda expressions.

• Streams provide a way to work with sequences of elements efficiently.

• Default methods allow interfaces to have methods with implementation.

HashSet is a collection that stores unique elements using hashing.

• Uses hashing to store elements for fast retrieval

• Does not allow duplicate elements

• Does not maintain insertion order

• Example: HashSet<String> set = new HashSet<>(); set.add("apple");

Kafka topics are categories to which messages are published by producers and from which consumers can read messages.

• Topics are used to organize and categorize messages in Kafka.

• Each topic can have multiple partitions to allow for parallel processing.

• Topics can have different retention policies and configurations.

• Examples: 'user_activity', 'order_updates', 'payment_events'