Barclays Java Developer Interview

Here’s a detailed guide for a Barclays Senior Java Developer Interview, including real-world-style questions, categorized by topic, along with sample answers and code where needed.

🔷 Overview: What to Expect

Interview Rounds (Typical):

1. Online Coding Test — HackerRank/CodeSignal-style
2. Technical Round 1 (Core Java) — OOP, multithreading, collections
3. Technical Round 2 (Spring + Microservices) — Spring Boot, REST, design
4. System Design Round — Design a scalable backend system
5. Behavioral + Managerial — STAR-based questions, team/project fit

🔹 Round 1: Core Java Questions

1. How does HashMap work internally in Java?

Answer:

• HashMap stores key-value pairs.
• Uses hashing: hashCode() and equals() methods.
• Handles collisions using chaining (LinkedList or TreeNode).
• Buckets are resized when load factor exceeds threshold (default 0.75).

Map<String, String> map = new HashMap<>();
map.put("name", "Sumit");