Oracle Interview Experience – Selected Candidate (Detailed Rounds)

Cracking an Oracle interview requires a deep understanding of core computer science fundamentals, problem-solving skills, and a strong grasp of Java concepts, data structures, algorithms, and system design.
Below is a detailed breakdown of the Oracle interview experience from a successfully selected candidate.

🔍 Round 1 – Technical + Core Java Concepts

Coding Problem

1. Smallest Subarray Problem

   • Problem: Given a string S and a string T, find the length of the smallest contiguous subarray of S that contains all the characters in T.
     (Characters in T can appear in any order.)

Core Java & OOPs Questions

• Covariant return types in Java.

• Exception hierarchy in Java.

• Can we use try without catch?

• Explain HashMap and its internal working (buckets, hashing, and collision resolution).

• What methods are present inside the Object class?

• Use of hashCode() and equals() in Object. How do they work internally?

• Why do we implement our own hashCode() if Java already provides a default implementation?

• Volatile keyword: What is it, and why is it used?

• What is the Stack memory in Java and its purpose?

• Immutable classes: What are they, and how can we implement them?

• Differences between ArrayList vs LinkedList.

  • When should you choose one over the other?

• What is ConcurrentModificationException?

  • What are fail-fast and fail-safe iterators?

• What is CopyOnWriteArrayList?

• Difference between final, finally, and finalize().

• Comparable vs Comparator: When and how to use them?

⚙️ Round 2 – Data Structures + SQL

Coding Problems

1. Implement a queue using a linked list.

2. Convert this queue into a stack.

3. From an employee table, find the name of the employee with the 2nd largest salary (SQL query).

4. How do you find the Nth largest element in Java?

5. Population problem:

   • Starting population in 1970 = 100.

   • Given the number of births and deaths per year, find the maximum population between 1970 and 2025.

📐 Round 3 – OOPS, SQL & Optimal Code

Conceptual Questions

• Explain OOPs concepts (Encapsulation, Inheritance, Abstraction, Polymorphism) with real-world examples.

• Types of exceptions in Java with examples.

• Error vs Exception: Key differences.

• Explain all the parts of a SELECT SQL query (SELECT, WHERE, GROUP BY, ORDER BY, etc.).

Coding Problems

• Write optimal code for calculating the sum of all rows and columns in a matrix (optimize both time and space).

• Write code to calculate the sums of diagonals of a matrix using O(N) time complexity.

💡 Round 4 – Advanced Coding + System Design

Design Patterns & Architecture

• Write code for all design patterns you have used in projects.

• Can we use a public constructor for a singleton class?

• Can REST APIs be used for asynchronous requests?

• How do you handle validation of requests?

• Difference between Authentication vs Authorization.

Multi-threading & Problem Solving

• Write a program to handle two different user inputs:

  • User1: Keep asking for number inputs until -1 is entered, then output the sum.

  • User2: Keep asking for string inputs until Z is entered, then output the final string.

  • Condition: Do this using two threads, where each operation can be picked up by any thread.

• Write a program to check a checkbox if all its children are checked (3-tier structure).

Java & Core Concepts

• Explain Serialization.

• What are marker interfaces? Can we create our own?

• Difference between interfaces and abstract classes with examples of Java-provided ones.

• Can abstract classes have zero abstract methods?

• What is Cloneable? Explain deep clone vs shallow clone in depth.

• Explain the Exception Hierarchy in Java.

• String vs StringBuffer vs StringBuilder: When to use which?

• Explain the String pool and immutability.

🎯 Key Takeaways

1. Java Mastery: Most rounds focus heavily on Java fundamentals like OOPs, Collections, Concurrency, and Memory Management.

2. Problem Solving: Be prepared for coding questions on data structures (Linked List, Stack, Queue, Matrix problems).

3. System Design & Patterns: A good understanding of design patterns and multi-threading is crucial.

4. SQL & Database Concepts: Query optimization and real-world database problems are common.

Preparation Tips

• Revise Java collections, multi-threading, and exception handling.

• Practice coding problems (arrays, strings, and matrix).

• Review system design basics (singleton, factory, observer, etc.).

• Brush up SQL queries (GROUP BY, RANK, LIMIT, etc.).

Oracle Hiring – Software Developer 1 | India | July 2025

Oracle, a global leader in cloud solutions and technology innovation, is hiring Software Developer 1 for its Product Development team. This is an excellent opportunity for candidates with 0 to 2+ years of experience looking to kickstart their careers in software development.

📌 Job Overview

🧠 Job Description

As a member of Oracle’s software engineering division, you will:

• Enhance and debug existing software applications.

• Develop and design data-driven reports using SQL.

• Gather requirements, plan tasks, and collaborate with stakeholders.

• Participate in technical design discussions.

• Perform debugging, root cause analysis, and documentation.

• Suggest team-level process improvements.

• Gain a deep understanding of healthcare workflows and the Millennium data model.

• Support software releases and operations.

🎓 Qualifications

🌟 Why Join Oracle?

• Global leader with 40+ years of innovation.

• Opportunities to work on cutting-edge technology.

• Inclusive workforce that promotes diversity and career growth.

• Competitive benefits including medical, insurance, and retirement plans.

• Strong focus on work-life balance and community engagement through volunteer programs.

💼 Career Level

IC1 (Entry Level).

⚠️ Important Information

• Visa/work permit sponsorship is not available for this position.

• Willingness to work irregular hours as needed

Click Here to Apply Now Oracle Software Developer 1