Three rounds were conducted for the interview:

• 1st round: Technical (written Hackerrank test). There were two questions; one was on Data Structures and Algorithms, and the second was on Java REST knowledge and code proficiency.
• 2nd round: Java and Design Patterns.
• 3rd round: Analytical and Unit Testing.

Here's the text to clean up:

1. Given an array of 0's and 1's, how many 0's need to be flipped consecutively to make the maximum number of 1's?
2. Given two API details, one with company-wise stock prices and another with holdings, calculate the total asset value on a particular date. The APIs were of two kinds: one paginated and one returning all data at once. It was required to implement runnable code with REST call logic, accessing the APIs and calculating the total asset value on a specific day.

Face-to-Face Round:

1. What is the Observer design pattern?
2. How would you approach optimizing the performance of an on-premise Java server?
3. Double-checked locking.
4. Need for immutable classes.

Last Round: Write a unit test case for HackerRank test question 1.