Recently I attended a Java Backend Developer interview (4+ years experience).

Sharing some of the questions that were asked. Hope it helps others preparing for similar roles.

Round 1 – Coding + Core Java + Spring Boot Duration (40 mins)

• Find the first non-repeated character in a string • OOPs concepts in detail (Encapsulation, Inheritance, Polymorphism, Abstraction) • Coding question: Can a private method in parent be overridden in child? Explain with code • Method overloading in child class – coding example • Connection Pooling in Java / Spring Boot • Spring Boot Bean Lifecycle • Difference between @Component and @Service

Round 2 – Advanced Java + Coding + System Design (Duration 1hr 20 minutes)

• OOPs concepts discussion • REST APIs concepts and best practices • Type Erasure in Generics (Java Generics concept) • Coding problem: Sort strings by length, and if length is same sort alphabetically • What will be the output of: "String str = "java.code" "str.replaceAll(".", "__");" • Immutable class in Java – how to design • Singleton class implementation • In constructor, can we write logic other than initializing fields? • Design patterns used in your projects • Fault tolerance – Circuit Breaker pattern in Microservices • SQL Question: Find average salary and 2nd highest average salary • How to use @EmbeddedId in JPA • How to resolve NoUniqueBeanDefinitionException.

And many cross questions.

Round 3 - Hackerrank Assessment

1) Functionality implmentation based on Oops concept successfully completed. 2) Medium level question 4 out of 7 test case passed.

Round 4 - Management round.

Project Related and tech stack related questions.

Result - REJECTED .

Despite the good interview where 80-85% questions i answered correctly I was not able to clear.

Learning - Sometimes your best interview also can lead to rejection so just focus on next interview rather than thinking about previous Results 😊

Hope this helps Java developers preparing for backend interviews.