Most Difficult Java 8 Stream Question Every Backend Developer Must Solve! | Code Decode

In this video of code decode we have covered most difficult java 8 scenario based interview questions Udemy Course Discounted Link https://www.udemy.com/course/master-spring-boot-microservice-angular-with-k8s-cicd-aws/?couponCode=APRIL2025 Top Java 8 scenario based interview questions E-Commerce Java 8 Streams – Real-World Scenarios and Solutions This collection of Java 8 Stream-based scenarios showcases how to apply functional programming to solve real-world problems in an e-commerce platform. Each use case is designed to reflect challenges commonly faced in backend systems, such as inventory tracking, customer behavior analysis, dynamic pricing, and order filtering. These solutions prioritize performance, readability, and clean design, making them both interview-ready and production-friendly. 1️⃣ Generate Category-wise Sales Report You are tasked with generating a category-wise product sales report for the last 24 hours, with multiple filtering rules: Consider only orders with a total value ₹500. Exclude any products marked as "out of stock". Group the filtered products by category. Calculate the total quantity sold per category. Return a result sorted by quantity in descending order. ✅ Solution: Using a combination of filter, flatMap, groupingBy, and sorting via streams, the code provides a concise way to compute the required report using LinkedHashMap to maintain sorted order. 2️⃣ Detect Orders with Stock Issues While processing orders, you must identify which orders exceed the available stock for any product: You have a Map String, Integer representing the available stock per product. Each order contains a list of Product objects with productId and quantity. ✅ Solution: By using nested stream() and anyMatch, you can efficiently detect problematic orders where ordered quantity stock. This approach is ideal for inventory validation logic before confirming an order. Mock Interview Playlist: https://www.youtube.com/playlist?list=PLyHJZXNdCXsdKpIT19C1nlZH_HROXyROF Most Asked Core Java Interview Questions and Answers: https://youtube.com/playlist?list=PLyHJZXNdCXscoyL5XEZoHHZ86_6h3GWE1 Advance Java Interview Questions and Answers: https://youtube.com/playlist?list=PLyHJZXNdCXsexOO1VQ4vs-BM2-8CKrixd Java 8 Interview Questions and Answers: https://youtube.com/playlist?list=PLyHJZXNdCXsdeusn4OM33415DCMQ6sUKy Hibernate Interview Questions and Answers: https://youtube.com/playlist?list=PLyHJZXNdCXsdC-p2186C6NO4FpadnCC_q Spring Boot Interview Questions and Answers: https://youtube.com/playlist?list=PLyHJZXNdCXsexOO1VQ4vs-BM2-8CKrixd Angular Playlist: https://www.youtube.com/watch?v=CAl7RQSdq2Q&list=PLyHJZXNdCXsfxRtDwtGkDD_lLfTWc1g0i SQL Playlist: https://www.youtube.com/playlist?list=PLyHJZXNdCXse86eLuwy5uZohd_bddE9Ni GIT: https://youtube.com/playlist?list=PLyHJZXNdCXscpl6pxOnL2lRWJlzvzjyZE Subscriber and Follow Code Decode Subscriber Code Decode: https://www.youtube.com/c/CodeDecode?sub_confirmation=1 LinkedIn : https://www.linkedin.com/in/codedecodeyoutube/ Instagram: https://www.instagram.com/codedecode25/ #java8 #codedecode #interviewquestions