I received a call from Oracle on April 15, 2021. I assume my resume was picked up from Naukri.

I was asked some basic questions to see if I was interested in their opening and if my experience aligned with their needs.

There were four technical rounds. The feedback from the initial three rounds was used to decide whether to proceed to a fourth round.

First round was set up on April 16, 2021.

• Had some basic questions on Java collections.
  • What and when do we use ArrayList and HashMap.
  • How to insert data into and how to iterate on those two data structures.
• A couple of competitive coding questions, where coming up with an optimal solution was the goal. Pseudo-code was sufficient.
• A simple recursion-based question.
• Given a table, fetch the data by writing a SQL query. The question was designed to utilize joins and aggregate functions.
• Difference between POST and PATCH methods.

Second round was set up on April 19, 2021.

This round was almost similar to the first round, but the questions were a little deeper and more twisted.

• Had a competitive coding-style question.
• A recursion-based question. Here, they interrupted and questioned to know my understanding of how recursion works.
• SQL query question.
• Few Java OOPS concepts-based questions.

Third round happened on April 20, 2021.

• In this round, I had to explain my current role and responsibilities.
• About the project that I am currently working on.
• Then, the questions turned out to be system design-based. Questions were like, "How will I scale the current system for more users?" and "What could be the cons and bottlenecks?"
• Difference between JRE and JVM.
• How does the garbage collector work.

Fourth round was on April 22, 2021.

• The round started with me briefing on my current project and the work I do.
• Few questions on why it was designed the way it is.
• Then, what design patterns I know.
  • I explained Singleton with a quick Java code for the same. There were a couple of questions like, "What would happen if the constructor is made public and the instance initialization is done in the constructor rather than having a static getInstance() method?"
  • Then, explained Factory and Builder patterns with Java code.
• What is cloning?
• What is serialization?
• What is constructor chaining?
• What is reflection?
• What is the difference between HashMap and Hashtable?