Lets Prepare
What is JPA? Java Persistence API (JPA) is a specification for managing relational data in Java applications. It provides an abstraction layer for object-relational mapping (ORM) and allows developers to interact with databases using Java objects rather than writing SQL queries manually. 1. Key Features of JPA 2. JPA Components a. Entity Entities are Java objects representing database tables. b. EntityManager The EntityManager is used to interact with the database.…
What is PIVOT in Databases? PIVOT is a technique used in SQL to transform row data into columns, making it useful for reporting and data visualization. Different databases implement pivoting differently. 1. Example Table (Sales Data) Before explaining the implementation, consider the following Sales table: Product Year Sales A 2023 100 B 2023 200 A 2024 150 B 2024 250 Expected Output (Pivoted Table): Product 2023 2024 A 100 150…
ConcurrentHashMap in Java is a thread-safe, high-performance alternative to HashMap that uses Compare-And-Swap (CAS) operations to achieve lock-free updates for certain methods. 1. What is CAS (Compare-And-Swap)? Compare-And-Swap (CAS) is an atomic operation that: Why CAS? 2. CAS-Based Methods in ConcurrentHashMap 1. putIfAbsent(K key, V value) 2. replace(K key, V oldValue, V newValue) 3. compute(K key, BiFunction<K, V, V> remappingFunction) 4. computeIfAbsent(K key, Function<K, V> mappingFunction) 5. computeIfPresent(K key, BiFunction<K,…
1. Introduction In system design, databases must be chosen based on the requirements of consistency, availability, and partition tolerance. Two key concepts guide this decision: 2. ACID Properties ACID properties define how traditional relational databases (SQL) maintain reliability and correctness. 3. CAP Theorem CAP Theorem states that in a distributed system, a database can achieve at most two of the following three properties: CAP Combinations and Database Types Category Ensures…
1. Overview This document provides an overview of a Microservices Architecture implemented with Spring Boot 3. The architecture includes key components such as API Gateway, Load Balancer, Service Discovery, Databases, Message Broker, Caching, Monitoring, and Logging. 2. Architecture Diagram Below is a high-level architecture diagram representing the microservices setup: 2.1 Diagram: Flow Between API Gateway, Load Balancer, and Service Discovery [Client] → [API Gateway] → [Load Balancer] → [Service Discovery]…
1. Introduction Java provides several concurrent collections under the java.util.concurrent package, which are designed for multi-threaded environments. These collections are optimized for thread safety and provide better performance compared to traditional synchronized collections. 2. ConcurrentHashMap Functions: Internal Working: 3. CopyOnWriteArrayList Functions: Internal Working: 4. CopyOnWriteArraySet Functions: Internal Working: 5. ConcurrentLinkedQueue Functions: Internal Working: 6. ConcurrentLinkedDeque Functions: Internal Working: 7. BlockingQueue Implementations Types of BlockingQueue: Queue Type Ordering Blocking Behavior ArrayBlockingQueue…
Introduction A LinkedHashMap in Java is a part of the java.util package and is used to store key-value pairs while maintaining insertion order. It extends HashMap and uses a doubly linked list to preserve the order of elements. Unlike HashMap, which does not guarantee any specific iteration order, LinkedHashMap maintains the order in which elements were inserted, making it useful for caching and ordering-sensitive applications. 1. Data Structure Used LinkedHashMap…
Introduction An ArrayDeque in Java is a part of the java.util package and is used as a resizable, double-ended queue (deque). It allows adding and removing elements from both ends efficiently and is faster than LinkedList for stack and queue operations. 1. Data Structure Used ArrayDeque is implemented using a circular array, which allows efficient insertions and deletions from both ends. Implementation in Java: 2. How Elements are Stored and…
Introduction A PriorityQueue in Java is a part of the java.util package and is used to store elements in a priority-based order. Unlike a normal queue (FIFO), PriorityQueue orders its elements based on natural ordering (for Comparable objects) or custom order defined by a Comparator. 1. Data Structure Used PriorityQueue is implemented using a binary heap, which ensures efficient retrieval of the highest or lowest priority element. Implementation in Java:…
Introduction A TreeSet in Java is a part of the java.util package and is used to store unique elements in sorted order. Unlike HashSet, which does not maintain order, TreeSet is implemented using a self-balancing Red-Black Tree, ensuring that elements are always stored in ascending order or a custom order defined by a comparator. 1. Data Structure Used TreeSet is implemented using a TreeMap, which internally uses a Red-Black Tree…