Array is a fixed-size data structure while ArrayList is a dynamic data structure in Java.

• Array is a basic data structure in Java that stores a fixed-size sequential collection of elements of the same type.

• ArrayList is a dynamic data structure that can grow or shrink in size as needed.

• Arrays are faster and more efficient for accessing elements, while ArrayLists are more flexible and easier to use.

• Example: int[] arr = new int[5]; ArrayList list = new ArrayList<>();

• Example: arr[...read more

Multithreading allows multiple threads to run concurrently, improving performance and responsiveness.

• Multithreading is useful for tasks that can be split into smaller, independent parts.

• It can improve performance by allowing multiple threads to execute simultaneously.

• It can also improve responsiveness by allowing the UI thread to remain responsive while other tasks are running in the background.

• Examples include downloading files while the user continues to interact with the a...read more

application.properties is used to store configuration settings for Java applications.

• Centralized storage for configuration settings

• Easy to update without changing code

• Allows for different configurations for different environments (development, testing, production)

• Can be used to store database connection details, API keys, logging settings, etc.

Data transfer between components in Angular can be achieved using input/output properties, services, and state management libraries like NgRx.

• Use @Input and @Output decorators to pass data between parent and child components.

• Create a service to share data between components that are not directly related.

• Utilize state management libraries like NgRx for managing application state and sharing data between components.

• Use event emitters to communicate between components.

• Consider u...read more

Plugins in Spring Boot are external modules that can be easily integrated into the application to add new functionalities.

• Plugins in Spring Boot are typically implemented as Spring beans that can be dynamically loaded and executed at runtime.

• They can be used to extend the functionality of the application without modifying the core codebase.

• Examples of plugins in Spring Boot include custom authentication providers, logging frameworks, and database connectors.

C programming language has 5 primary data types: int, float, double, char, and void.

• Primary data types in C are int, float, double, char, and void.

• Examples: int num = 10; float value = 3.14; char letter = 'A';

• Additional data types like long, short, signed, unsigned, etc. can be derived from these primary types.

Java is a high-level programming language known for its portability, security, and versatility.

• Java is an object-oriented language, meaning it focuses on creating objects that interact with each other.

• It is platform-independent, meaning Java programs can run on any device that has a Java Virtual Machine (JVM).

• Java is known for its security features, such as automatic memory management and built-in exception handling.

• Popular Java frameworks include Spring, Hibernate, and Apach...read more

Array is a fixed-size data structure while ArrayList is a dynamic-size data structure.

• Array is a primitive data type while ArrayList is a class in Java.

• Array has a fixed size while ArrayList can grow or shrink dynamically.

• Array can hold only homogeneous data types while ArrayList can hold heterogeneous data types.

• Array uses [] to declare while ArrayList uses <>.

• Example: int[] arr = new int[5]; ArrayList list = new ArrayList<>();

Component annotations are used in Java to declare a class as a component of Spring framework.

• @Component - declares a class as a Spring component

• @Repository - declares a class as a data repository

• @Service - declares a class as a service component

• @Controller - declares a class as a controller component

Capacity 16 with only one null element means there are 15 non-null elements in the array.

• The array has a total capacity of 16 elements.

• There is only one null element in the array.

• This implies that there are 15 non-null elements in the array.

Collection framework in Java is a set of classes and interfaces that provide a standard way to store and manipulate groups of objects.

• It provides interfaces like List, Set, and Map to store collections of objects.

• Classes like ArrayList, LinkedList, HashSet, and HashMap implement these interfaces.

• Collections framework simplifies the process of storing, retrieving, and manipulating data in Java programs.

Java is a programming language while Hibernate is an ORM tool for Java.

• Java is an object-oriented programming language used for developing applications.

• Hibernate is an ORM tool that simplifies the process of mapping Java objects to database tables.

• Hibernate provides a framework for querying and manipulating data from a database using Java objects.

• Hibernate supports various database management systems such as MySQL, Oracle, and PostgreSQL.

• Hibernate reduces the amount of boiler...read more

JDK stands for Java Development Kit, it is a software development kit used for developing Java applications.

• JDK includes tools for developing, debugging, and monitoring Java applications.

• It contains JRE (Java Runtime Environment) which is necessary for running Java programs.

• JDK also includes a compiler, debugger, and other tools needed for Java development.

• Examples of JDK versions include JDK 8, JDK 11, and JDK 15.

Hibernate is an open-source Java framework that simplifies the development of database interactions in Java applications.

• Hibernate is an Object-Relational Mapping (ORM) tool that maps Java objects to database tables.

• It provides a way to perform database operations using Java objects instead of writing SQL queries.

• Hibernate handles the mapping of Java classes to database tables and vice versa, as well as the generation of SQL queries.

• It helps in managing the database connectio...read more

Garbage collection is the process of automatically reclaiming memory occupied by objects that are no longer in use by the program.

• Garbage collection is a feature in Java that automatically manages memory by deallocating memory for objects that are no longer needed.

• It helps in preventing memory leaks and ensures efficient memory usage.

• Garbage collection runs in the background and identifies objects that are no longer reachable by the program.

• Examples of garbage collection algo...read more

Method overloading is when multiple methods in the same class have the same name but different parameters.

• Allows multiple methods with the same name but different parameters to be defined in a class.

• Parameters can differ in number, type, or order.

• Example: void print(int a) and void print(String s) are overloaded methods in the same class.

Java is a popular programming language known for its features like platform independence, object-oriented programming, and automatic memory management.

• Java is platform-independent, meaning that it can run on any platform that has a Java Virtual Machine (JVM) installed.

• Java supports object-oriented programming (OOP) concepts like encapsulation, inheritance, and polymorphism.

• Java has automatic memory management, which means that the programmer does not have to manually allocate...read more

A classLoader is a part of the Java Runtime Environment that dynamically loads Java classes into the Java Virtual Machine.

• ClassLoader is responsible for loading classes at runtime in Java.

• It follows a delegation hierarchy to search for classes.

• There are different types of class loaders like Bootstrap, Extension, and System class loaders.

• Custom class loaders can be created to load classes from different sources like network or database.

Polymorphism is the ability of an object to take on multiple forms.

• Polymorphism allows objects of different classes to be treated as objects of a common superclass.

• There are two types of polymorphism: compile-time (method overloading) and runtime (method overriding).

• Example: Animal superclass with Dog and Cat subclasses, both overriding the makeSound() method.

Find the median of a subarray in a given array.

• Sort the subarray and find the middle element for odd length subarrays.

• For even length subarrays, find the average of the middle two elements.

• Use a sliding window approach to iterate through all subarrays.

Failsafe is a mechanism to handle failures without affecting the system's overall functionality, while failfast immediately stops the system upon encountering an error.

• Failsafe is used to ensure that a system remains operational even in the face of failures, by providing alternative paths or fallback options.

• Failfast is a strategy where the system stops as soon as an error is detected, to prevent further damage or incorrect results.

• Example: Failsafe can be implemented in a di...read more

Count the frequency of numbers in an array of strings.

• Iterate through the array and use a HashMap to store the count of each number.

• Handle edge cases like empty array or null values.

• Return the HashMap with number frequencies.

HashMap works internally using an array of buckets to store key-value pairs, with each bucket containing a linked list of entries.

• HashMap uses hashing to determine the index of the bucket where the key-value pair should be stored.

• If multiple key-value pairs hash to the same index, they are stored in a linked list within that bucket.

• When retrieving a value, the key's hash code is used to find the correct bucket, then the linked list is traversed to find the matching key.

• HashMa...read more

Array is a fixed size data structure while ArrayList is a dynamic size data structure in Java.

• Array is a primitive data type while ArrayList is a class in Java.

• Array can hold only homogeneous data types while ArrayList can hold heterogeneous data types.

• Array needs to be initialized with a fixed size while ArrayList can be initialized without a size.

• Array uses [] brackets to declare while ArrayList uses <> brackets to declare.

• Array is faster than ArrayList for accessing elemen...read more

Marker interface is an interface with no methods, used to mark a class as having a certain property or behavior.

• Marker interfaces are used for metadata purposes.

• They are used to provide information to the compiler or runtime environment.

• Examples of marker interfaces in Java include Serializable, Cloneable, and Remote.

• Marker interfaces can also be used to enforce design patterns, such as the Decorator pattern.

Multi threading is the ability of a program to execute multiple threads concurrently, allowing for better performance and responsiveness.

• Allows multiple tasks to be performed simultaneously

• Improves performance by utilizing multiple CPU cores

• Can lead to synchronization issues if not handled properly

• Example: A web server handling multiple client requests concurrently

Microservices communicate through lightweight protocols like HTTP, messaging queues, and RPC.

• HTTP: RESTful APIs are commonly used for communication between microservices.

• Messaging queues: Services can communicate asynchronously through message brokers like RabbitMQ or Kafka.

• RPC (Remote Procedure Call): Services can directly call each other's functions over the network.

Rest controller is used in Spring MVC for RESTful web services, while controller is used for general web requests.

• Rest controller is used for creating RESTful web services in Spring MVC

• Controller is used for handling general web requests in Spring MVC

• Rest controller uses @RestController annotation, while controller uses @Controller annotation

• Rest controller returns data in JSON or XML format, while controller returns data in HTML format

String in Java is immutable because once created, its value cannot be changed.

• String objects are constant and their values cannot be changed after they are created.

• Any operation that appears to modify a String actually creates a new String object.

• Example: String str = "Hello"; str.concat(" World"); // This does not change the original value of str.

Comparator is used to compare objects of a class, while Comparable is implemented by a class to define its natural ordering.

• Comparator is an interface that can be used to define custom comparison logic for objects.

• Comparable is an interface that is implemented by a class to define its natural ordering.

• Comparator can be used to sort objects in different ways, even if they don't implement Comparable.

• Comparable allows objects to be sorted based on their natural ordering, such as...read more

Java uses automatic memory management through garbage collection to allocate and deallocate memory for objects.

• Java uses garbage collection to automatically manage memory by deallocating objects that are no longer in use.

• Memory is divided into stack and heap. Stack stores primitive types and references to objects, while heap stores objects.

• Java automatically allocates memory for objects on the heap and deallocates memory when the object is no longer referenced.

• Developers can ...read more

ArrayList is implemented as a resizable array, LinkedList is implemented as a doubly linked list.

• ArrayList provides fast random access, LinkedList provides fast insertion and deletion.

• ArrayList uses more memory as it is a dynamic array, LinkedList uses more memory for storing references to next and previous elements.

• ArrayList is better for storing and accessing data sequentially, LinkedList is better for manipulating data frequently.

Literals in Java are fixed values that are directly used in the code.

• Literals can be of various types such as integer literals, floating-point literals, character literals, string literals, boolean literals, and null literals.

• Examples: int num = 10; double pi = 3.14; char letter = 'A'; String name = "John"; boolean flag = true; Object obj = null;

Collection framework is a set of classes and interfaces that provide a way to store and manipulate groups of objects.

• It includes interfaces like List, Set, and Map

• It provides implementations like ArrayList, HashSet, and HashMap

• It simplifies the process of storing and manipulating data

• It allows for easy iteration and sorting of collections

• Example: List names = new ArrayList<>();

• Example: Map ages = new HashMap<>();

Thread is a lightweight sub-process, a separate path of execution within a program.

• Threads allow concurrent execution of two or more parts of a program.

• Java provides built-in support for multithreading through the Thread class and Runnable interface.

• Threads can be created by extending the Thread class or implementing the Runnable interface.

• Thread.sleep() method is used to pause the execution of a thread for a specified amount of time.

• Thread.join() method is used to wait for a...read more

Microservices is an architectural style that structures an application as a collection of small, independent services.

• Microservices are independently deployable and scalable.

• Each microservice focuses on a specific business capability.

• Communication between microservices is usually done through APIs.

• Microservices can be developed using different programming languages and technologies.

• Examples of companies using microservices include Netflix, Amazon, and Uber.

Constructor chaining is calling one constructor from another constructor within the same class.

• It allows to reuse the code of one constructor in another constructor.

• It is achieved using the 'this' keyword followed by the constructor parameters.

• It can be used to set default values or to initialize variables before calling another constructor.

• Example: public MyClass(int x) { this(x, 0); } public MyClass(int x, int y) { this.x = x; this.y = y; }

Singleton class is a class that allows only one instance of itself to be created and provides a global point of access to that instance.

• Singleton class restricts the instantiation of a class to one object.

• It provides a way to access its unique instance globally.

• Commonly used in scenarios where only one instance of a class is needed, such as database connections or configuration settings.

CSS stands for Cascading Style Sheets. It is a language used for styling web pages.

• CSS is used to control the layout and appearance of HTML elements on a webpage

• There are three types of CSS: inline, internal, and external

• Inline CSS is applied directly to an HTML element using the style attribute, e.g.

• Internal CSS is defined within the

The equals() method is used to compare the contents of two objects for equality.

• The equals() method is a method of the Object class in Java.

• It is used to compare the contents of two objects for equality.

• The default implementation of equals() in the Object class compares memory addresses, so it is often overridden in custom classes to compare content.

• Example: String class overrides equals() method to compare the content of two strings.

Synchronized keyword is used in Java to control access to shared resources by multiple threads.

• Synchronized keyword can be applied to methods or code blocks to ensure only one thread can access the synchronized code at a time.

• It prevents race conditions and ensures thread safety by creating a lock on the object or class.

• Example: synchronized void myMethod() { // synchronized code block }

Executor framework is a framework in Java that provides a way to manage and execute tasks asynchronously.

• Allows for managing thread execution in a more efficient way

• Provides a way to decouple task submission from task execution

• Supports various types of executors like ThreadPoolExecutor and ScheduledExecutorService

• Helps in handling tasks concurrently and asynchronously

BlockingQueue is an interface in Java that represents a queue which supports operations that wait for the queue to become non-empty when retrieving an element and wait for space to become available in the queue when adding an element.

• BlockingQueue is part of the java.util.concurrent package.

• It is used for implementing producer-consumer scenarios where multiple threads are involved.

• Methods like put() and take() are used to add and remove elements from the queue, respectively.

API Gateway implementation is a centralized service that routes, manages, and secures API calls.

• API Gateway acts as a single entry point for all API calls

• It can handle authentication, rate limiting, caching, and request/response transformations

• Examples include AWS API Gateway, Apigee, Kong

Circuit breaker is a design pattern used to prevent system overload by temporarily stopping requests to a failing service.

• Circuit breaker monitors requests to a service and opens when the service fails repeatedly.

• It helps prevent cascading failures and allows the system to gracefully degrade.

• Once the circuit breaker is open, it can periodically check if the service has recovered before allowing requests again.

Runnable is a functional interface with a single run() method, while Callable is a functional interface with a single call() method.

• Runnable is used for tasks that do not return a result, while Callable is used for tasks that return a result.

• Callable can throw checked exceptions, while Runnable cannot.

• Callable returns a Future object, which can be used to retrieve the result of the computation.

• Example: Runnable - executing a task in a separate thread without returning a resul...read more

Runnable and Callable are interfaces in Java for creating threads. Runnable is used for tasks that don't return a result, while Callable is used for tasks that return a result.

• Runnable is a functional interface with a single run() method, while Callable is a generic interface with a single call() method.

• Runnable tasks are executed using the void run() method, while Callable tasks are executed using the Future call() method.

• Runnable tasks cannot throw checked exceptions, while...read more

Streams in Java are sequences of elements that support functional-style operations. They provide advantages like lazy evaluation and parallel processing.

• Streams allow for functional-style operations like map, filter, and reduce.

• They support lazy evaluation, meaning elements are processed only when needed.

• Streams can be easily parallelized to improve performance.

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

Service discovery is the process of automatically finding and connecting to services in a network.

• Service discovery allows applications to dynamically locate and communicate with services without hardcoding their locations.

• It helps in load balancing, fault tolerance, and scalability by enabling services to be added or removed without manual intervention.

• Examples of service discovery tools include Consul, Eureka, and Zookeeper.

OOPs stands for Object-Oriented Programming. It is a programming paradigm based on the concept of objects.

• OOPs focuses on creating objects that contain both data and functions to manipulate that data.

• It emphasizes on encapsulation, inheritance, and polymorphism.

• Java, C++, Python, and Ruby are some of the popular OOPs languages.

• Example: A car can be considered as an object that has properties like color, model, and functions like start, stop, and accelerate.

Java programming structure refers to the organization of code in a Java program.

• Java programs are organized into classes, which contain methods and variables.

• Classes can be grouped into packages for better organization.

• Java follows a strict syntax and structure, with curly braces indicating code blocks.

• Code must be compiled before it can be executed.

• Java programs follow an object-oriented programming paradigm.

Microservices are a software development technique where applications are composed of small, independent services that communicate over well-defined APIs.

• Microservices break down a large application into smaller, independent services

• Each service is responsible for a specific function and can be developed, deployed, and scaled independently

• Services communicate with each other over APIs, often using lightweight protocols like HTTP or messaging queues

• Microservices architecture p...read more

Containers in SpringBoot are used to manage and deploy Spring applications.

• Containers in SpringBoot provide a lightweight and portable way to package and run applications.

• They include all the necessary dependencies and configurations needed to run the application.

• Containers can be easily deployed and scaled using tools like Docker and Kubernetes.

• Examples of containers in SpringBoot include Docker containers running SpringBoot applications.

Spring Boot is an opinionated framework for building stand-alone, production-grade Spring-based Applications. Spring MVC is a part of the Spring Framework for building web applications.

• Spring Boot is an opinionated framework that simplifies the setup and configuration of Spring applications, while Spring MVC is a part of the Spring Framework that focuses on building web applications.

• Spring Boot provides embedded servers for deploying applications, whereas Spring MVC requires ...read more

HashMap is a data structure that stores key-value pairs and uses hashing to efficiently retrieve values based on keys.

• HashMap internally uses an array of linked lists to store key-value pairs.

• When a key-value pair is added, the key is hashed to determine the index in the array where it will be stored.

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

• HashMap allows one null key and multiple null values.

• Example: HashMap<String, Integer> map = n...read more

The synchronized keyword in Java is used to control access to shared resources by allowing only one thread to execute a synchronized block of code at a time.

• Synchronized keyword can be used with methods or blocks of code to ensure thread safety.

• It can be used to prevent race conditions and ensure data consistency in multi-threaded applications.

• Example: synchronized void myMethod() { // synchronized method implementation }

Java is a versatile programming language used for developing a wide range of applications, from web and mobile apps to enterprise software.

• Java is used for developing web applications, such as online banking systems and e-commerce websites.

• It is commonly used for creating mobile applications for Android devices.

• Java is also used for developing enterprise software, like customer relationship management (CRM) systems and supply chain management software.

JDBC is a low-level API for connecting to databases, while Hibernate is a high-level ORM framework.

• JDBC requires manual coding for CRUD operations, while Hibernate provides automatic mapping of objects to database tables.

• JDBC is more suitable for small-scale applications, while Hibernate is better for large-scale applications.

• Hibernate provides caching and lazy loading, which improves performance, while JDBC does not have these features.

• Hibernate supports inheritance mapping,...read more

Constructor is a special method that is used to initialize objects in Java.

• Constructor has the same name as the class name

• It does not have a return type

• It can be overloaded

• It is called automatically when an object is created

• Example: public class Car { public Car() { // constructor code here } }

Microservices are a software development technique where applications are broken down into smaller, independent services that communicate with each other.

• Microservices are small, independent services that work together to form a complete application

• Each microservice is responsible for a specific function or feature

• Microservices communicate with each other through APIs

• They can be developed, deployed, and scaled independently

• Examples of companies using microservices include Net...read more

A program to print the elements of an array of strings in reverse order.

• Declare an array of strings.

• Initialize the array with some values.

• Loop through the array in reverse order.

• Print each element of the array.

Java 8 introduced several new features including lambda expressions, streams, and functional interfaces.

• Lambda expressions allow for functional programming and simplify code.

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

• Functional interfaces allow for the use of lambda expressions.

• Default methods allow for adding methods to interfaces without breaking existing implementations.

• Date and time API improvements.

• Nashorn JavaScript engine.

• Parallel array so...read more

Java8 introduced several new features including lambda expressions, functional interfaces, streams, and default methods.

• Lambda expressions allow for more concise code by enabling functional programming.

• Functional interfaces are interfaces with a single abstract method, such as Runnable or Comparator.

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

• Default methods allow interfaces to have method implementations.

• Example: Lambda expression - (a, b) -...read more

JVM process is an instance of Java Virtual Machine that executes Java bytecode.

• JVM process is responsible for interpreting and executing Java bytecode.

• It manages memory, handles garbage collection, and provides runtime environment for Java programs.

• Examples of JVM implementations include Oracle HotSpot, OpenJ9, and GraalVM.

Java API works by providing a set of classes and interfaces that allow developers to interact with various functionalities and services.

• Java API provides a standardized way for developers to access and use pre-built classes and interfaces.

• Developers can use Java API to perform tasks such as file handling, networking, database access, and more.

• Java API documentation provides detailed information on how to use each class and interface, along with examples and best practices.

HTTP servlet is a Java class that extends the capabilities of servers that host applications accessed by HTTP protocol.

• HTTP servlet is a Java class that extends the capabilities of servers that host applications accessed by HTTP protocol

• It is used to handle HTTP requests and responses

• It provides methods to get information about the request and to send a response back to the client

• It can be used to create dynamic web pages, handle form data, and manage sessions

• Example: HttpSer...read more

Java is a versatile, platform-independent language with a vast community and extensive libraries.

• Java is object-oriented and easy to learn.

• It has a vast community and extensive libraries.

• It is platform-independent and can run on any device.

• Java is secure and reliable.

• It is used in various domains like web development, mobile app development, and enterprise applications.

• Examples: Android apps, Spring framework, Hadoop, Minecraft.

HashMap is a data structure that stores key-value pairs and uses hashing to efficiently retrieve values.

• HashMap uses hashing to store and retrieve key-value pairs.

• It allows null keys and values.

• HashMap does not maintain insertion order.

• Example: HashMap map = new HashMap<>();

Spring is a framework for building Java applications, while Spring Boot is a tool for quickly creating standalone Spring-based applications.

• Spring is a comprehensive framework that provides support for various functionalities like dependency injection, aspect-oriented programming, and more.

• Spring Boot is an opinionated tool that simplifies the setup and configuration of Spring applications, allowing developers to quickly create standalone applications with minimal configurati...read more

Truncate is a SQL command used to delete all rows from a table without logging the individual row deletions.

• Truncate is a DDL (Data Definition Language) command in SQL.

• It is used to quickly delete all rows from a table, but it does not log individual row deletions.

• Truncate is faster than using the DELETE command, as it does not generate individual row deletion logs.

• Truncate also resets any auto-incrementing keys in the table.

• Example: TRUNCATE TABLE table_name;

Functional interfaces in Java are interfaces with a single abstract method, used for lambda expressions.

• Consumer

• Supplier

• Predicate

• Function

Profiles in Java are configurations that define the capabilities of a Java platform.

• Profiles allow developers to target specific types of devices or applications.

• They help in reducing the size of the Java runtime environment by including only the necessary APIs.

• Examples include Java SE Embedded Profile for embedded devices and Java SE Compact Profile for resource-constrained environments.

Spring Boot is a framework that simplifies the development of Java applications by providing pre-configured settings and tools.

• Spring Boot eliminates the need for manual configuration by providing defaults for most settings.

• It allows for standalone Spring applications that can be started with a simple 'java -jar' command.

• Spring Boot includes embedded servers like Tomcat, Jetty, or Undertow for deploying web applications.

• It promotes convention over configuration, reducing the ...read more

Patch and put are HTTP methods used for updating resources on a server.

• PATCH is used to partially update a resource, while PUT is used to completely replace a resource.

• PATCH requests only include the changes that need to be made, while PUT requests require sending the entire updated resource.

• PATCH is often used for incremental updates, while PUT is used for full updates.

• Example: PATCH request to update the 'name' field of a user resource, and PUT request to replace the entire...read more

An array is a collection of similar type of elements stored in contiguous memory locations.

• Arrays can be of primitive data types or objects.

• Arrays have a fixed size and can be accessed using an index.

• Arrays can be multidimensional.

• Example: int[] arr = {1, 2, 3};

• Example: String[][] arr = { {"John", "Doe"}, {"Jane", "Doe"} };

OOPs concepts are the foundation of object-oriented programming, including inheritance, encapsulation, polymorphism, and abstraction.

• Inheritance: Allows a class to inherit properties and behavior from another class.

• Encapsulation: Bundling data and methods that operate on the data into a single unit.

• Polymorphism: Ability to present the same interface for different data types.

• Abstraction: Hiding the complex implementation details and showing only the necessary features.

String is a sequence of characters used to represent text in programming languages.

• Strings are immutable in Java, meaning their values cannot be changed once they are created.

• Strings can be created using double quotes or by calling the String constructor.

• String concatenation can be done using the '+' operator.

• Common methods for manipulating strings include length(), charAt(), substring(), toUpperCase(), toLowerCase().

API gateway is a server that acts as an API front-end, receiving API requests, enforcing throttling and security policies, passing requests to the back-end service, and then passing the response back to the requester.

• API gateway acts as a single entry point for all API requests

• It can handle tasks like authentication, authorization, rate limiting, caching, and request routing

• Examples of API gateways include Amazon API Gateway, Apigee, and Kong

Sorting array of strings

• Use Arrays.sort() method to sort the array in ascending order

• Use Comparator.reverseOrder() to sort the array in descending order

• Implement your own sorting algorithm if required

Java 8 introduced new features like lambda expressions, streams, default methods, and functional interfaces.

• Lambda expressions allow you to write code in a more concise way.

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

• Default methods allow interfaces to have method implementations.

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

JVM stands for Java Virtual Machine, which is an abstract computing machine that enables a computer to run Java programs.

• JVM is responsible for converting Java bytecode into machine code that can be executed by the computer's operating system.

• It provides a platform-independent execution environment for Java programs.

• JVM manages memory, handles garbage collection, and provides security features for Java applications.

OOPs (Object-Oriented Programming) is a programming paradigm based on the concept of objects, which can contain data and code.

• OOPs focuses on creating objects that interact with each other to solve a problem.

• Key principles include encapsulation, inheritance, polymorphism, and abstraction.

• Encapsulation involves bundling data and methods that operate on the data into a single unit.

• Inheritance allows a class to inherit properties and behavior from another class.

• Polymorphism allo...read more

OOPs is a programming paradigm based on the concept of objects.

• OOPs stands for Object-Oriented Programming.

• It focuses on creating objects that contain both data and functions.

• Encapsulation, Inheritance, and Polymorphism are the three main pillars of OOPs.

• Java, C++, Python, and Ruby are some of the popular OOPs languages.

• Example: A car can be an object with properties like color, model, and functions like start, stop, and accelerate.

Java is a popular programming language known for its platform independence and object-oriented approach.

• Java is a high-level, class-based, object-oriented programming language.

• It is designed to have as few implementation dependencies as possible, making it platform-independent.

• Java applications are typically compiled to bytecode that can run on any Java virtual machine (JVM).

HashMap is non-synchronized and allows null values, while hash table is synchronized and does not allow null values.

• HashMap is non-synchronized and not thread-safe, while hash table is synchronized and thread-safe.

• HashMap allows null values and one null key, while hash table does not allow null keys or values.

• HashMap is generally preferred for non-thread-safe applications, while hash table is used in thread-safe applications.

Spring Boot is a framework that simplifies the development of Spring applications by providing pre-configured settings and conventions.

• Spring Boot is opinionated and provides defaults for configuration, reducing the need for manual setup.

• Spring Boot includes embedded servers like Tomcat, Jetty, or Undertow, making it easy to deploy standalone applications.

• Spring Boot offers a variety of starters to quickly set up common dependencies and configurations.

• Spring Boot is ideal for...read more

Oops concepts are fundamental principles of object-oriented programming such as inheritance, polymorphism, encapsulation, and abstraction.

• Inheritance: Allows a class to inherit properties and behavior from another class.

• Polymorphism: Ability of an object to take on many forms.

• Encapsulation: Bundling of data with the methods that operate on that data.

• Abstraction: Hiding the complex implementation details and showing only the necessary features of an object.

The life cycle of multi-threading involves the creation, execution, and termination of threads.

• Threads are created using the Thread class or by implementing the Runnable interface

• Threads can be in various states such as new, runnable, blocked, waiting, timed waiting, or terminated

• Thread execution involves the start, run, and sleep methods

• Threads can communicate and synchronize using methods like wait, notify, and join

• Threads can be terminated using the stop or interrupt metho...read more

Java 8 introduced several new features including lambda expressions, functional interfaces, streams, and default methods in interfaces.

• Lambda expressions allow you to write code in a more concise and readable way.

• Functional interfaces are interfaces with a single abstract method, used for lambda expressions.

• Streams provide a way to work with sequences of elements in a functional style.

• Default methods in interfaces allow you to add new methods to interfaces without breaking ex...read more

OOPs is a programming paradigm based on the concept of objects that interact with each other.

• OOPs stands for Object-Oriented Programming.

• It focuses on creating objects that have properties and methods.

• Encapsulation, Inheritance, Polymorphism, and Abstraction are the four main pillars of OOPs.

• Java, C++, Python, and Ruby are some of the popular OOPs languages.

• Example: A car can be an object with properties like color, model, and methods like start, stop, and accelerate.

OOPs concepts are the foundation of object-oriented programming, including encapsulation, inheritance, polymorphism, and abstraction.

• Encapsulation: Bundling data and methods that operate on the data into a single unit (class).

• Inheritance: Allows a class to inherit properties and behavior from another class.

• Polymorphism: Ability to present the same interface for different data types.

• Abstraction: Hiding the complex implementation details and showing only the necessary features ...read more

HashSet is a collection that does not allow duplicate elements and does not guarantee the order of elements.

• HashSet implements the Set interface in Java.

• Elements are stored using a hash table.

• Addition, removal, and lookup operations have constant time complexity.

• Example: HashSet set = new HashSet<>();

• Example: set.add("apple");