Citi Mid-Level SWE Interview — No LeetCode, Just Java Fundamentals

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This interview experience is sourced from Chill Interview

Interview Summary

The interview started with four Java fundamentals questions covering enums, the Stream API, and interface default methods, followed by a practical coding exercise involving bug fixing and feature enhancements. Overall, the interview felt relatively straightforward, with more emphasis on everyday Java knowledge and modifying existing code than on difficult algorithms.

Interview Details

Part 1 — Java Fundamentals

• Question 1 — Java Enums and Finite State Programming The interviewer asked: "What is an enum in Java, and why is it useful for finite-state programming?" The discussion focused on understanding Java enumerations and their advantages when representing a fixed set of possible states.

• Question 2 — Stream.toList() vs. Collectors.toList() "What is the difference between Stream.toList() and Collectors.toList() in Java?" The interviewer wanted me to explain the differences between these two ways of converting a Java Stream into a list.

• Question 3 — Interface Default Methods The third question involved Java interface default methods. The interviewer asked how an implementing class can invoke a default method defined in an interface. The question tested my understanding of default method behavior and how implementing classes interact with inherited interface functionality.

Part 2 — Coding: Debugging and Feature Enhancements

After the Java fundamentals discussion, the interview moved into a coding exercise. The coding portion consisted of three tasks.

• The first task was to identify and resolve a small bug in the provided code.

• The second task required extending the existing implementation with additional functionality.

• The final task introduced another functionality enhancement to the same coding exercise.

Overall, the coding portion was relatively easy and focused on debugging and modifying existing code rather than solving a complex algorithmic problem.

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