Oracle Senior Application Developer Interview Questions, Process, and Tips

Round duration - 60 Minutes
Round difficulty - Medium

This round had 1 question related to DSA and then the majority of the questions were revolving around Java.

Q1. 
Convert a Binary Tree to its Sum Tree
Given a binary tree of integers, convert it to a sum tree where each node is replaced by the sum of the values of its left and right subtrees. Set leaf nodes to zero.
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Ans. 
Approach : 

1) Build the Sum Tree
1.1) Update the root data with the sum of the left and right children’s data given that the root itself is not null.
1.2) Check the left node and right node. If they are not null, take their sum and update the root data.
1.3) Extend this idea further by making a recursive call on to the left and right subtrees.

2) Do a pre order traversal.
2.1) To keep track of the node data in the preo...read more
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Q2. What is the garbage collector in Java?
Ans. 
Answer :

1) Garbage Collection in Java is a process by which the programs perform memory management automatically.

2) The Garbage Collector(GC) finds the unused objects and deletes them to reclaim the memory. I

3) In Java, dynamic memory allocation of objects is achieved using the new operator that uses some memory and the memory remains allocated until there are references for the use of the object.

4) When there are no r...read more
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Q3. Why is Java considered platform independent, while the Java Virtual Machine (JVM) is platform dependent?
Ans. 
JVM is platform dependent because it takes java byte code and generates byte code for the current operating system. So Java software is platform dependent but Java language is platform independent because different operating system have different JVMs.
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Q4. What do you understand by marker interfaces in Java?
Ans. 
Marker interfaces, also known as tagging interfaces are those interfaces that have no methods and constants defined in them. They are there for helping the compiler and JVM to get run time-related information regarding the objects.
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Round duration - 60 Minutes
Round difficulty - Medium

In this round, I had 2 questions of DSA where I had to first explain my approach with proper compleixt analysis and then write the pseudo code for both of them. After that, I was asked some questions from Java and MVC architecture.

Q1. 
LRU Cache Design Question
Design a data structure for a Least Recently Used (LRU) cache that supports the following operations:
1. get(key) - Return the value of the key if it exists in the cache; otherw...read more
Ans. 
Answer :

Structure of an LRU Cache :

1) In practice, LRU cache is a kind of Queue — if an element is reaccessed, it goes to the end of the eviction order.
2) This queue will have a specific capacity as the cache has a limited size. Whenever a new element is brought in, it is added at the head of the queue. When eviction happens, it happens from the tail of the queue.
3) Hitting data in the cache must be done in constant ti...read more
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Q2. 
Intersection of Linked List Problem
You are provided with two singly linked lists containing integers, where both lists converge at some node belonging to a third linked list.
Your task is to determine t...read more
Ans. 
Approach (Using 2-pointers) : 

1) Initialize two pointers ptr1 and ptr2 at the head1 and head2.
2) Traverse through the lists,one node at a time.
3) When ptr1 reaches the end of a list, then redirect it to the head2.
4) Similarly when ptr2 reaches the end of a list, redirect it the head1.
5) Once both of them go through reassigning, they will be equidistant from the collision point
6) If at any node ptr1 meets ptr2, the...read more
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Q3. Can you explain in brief the role of different MVC components?
Ans. 
The different MVC components have the following roles -
1) Presentation: This component takes care of the visual representation of a particular abstraction in the application.

2) Control: This component takes care of the consistency and uniformity between the abstraction within the system along with their presentation to the user. It is also responsible for communicating with all other controls within the MVC system.

3) A...read more
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Q4. How is routing handled in the MVC pattern?
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There is a group of routes called the RouteCollection, which consists of registered routes in the application. The RegisterRoutes method records the routes in this collection. A route defines a URL pattern and a handler to use if the request matches the pattern.

The first parameter to the MapRoute method is the name of the route. The second parameter will be the pattern to which the URL matches. The third parameter migh...read more
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Q5. Is it possible to import the same class or package twice in Java, and what happens during runtime?
Ans. 
It is possible to import a class or package more than once, however, it is redundant because the JVM internally loads the package or class only once.
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Round duration - 60 Minutes
Round difficulty - Medium

This round was inclined towards some Low Level Design Principles and some concepts from MVC.

Q1. Design a Railway Reservation System.
Ans. 
Tip 1 : Firstly, remember that the system design round is extremely open-ended and there’s no such thing as a standard answer. Even for the same question, you’ll have a totally different discussion with different interviewers.
Tip 2 : Before you jump into the solution always clarify all the assumptions you’re making at the beginning of the interview. Ask questions to identify the scope of the system. This will clear the...read more
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Q2. What is Spring MVC?
Ans. 
1) The Spring MVC or Spring Web MVC can be defined as a framework that provides a “Model View Controller” (MVC) architecture in the application as well as ready-components implemented for developing adjustable and adaptable web applications. 

2) It is actually a Java-based framework intended to build web applications. It works on the Model-View-Controller design approach. 

3) This framework also makes use of al...read more
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Q3. Can you define the concept of Filters in MVC?
Ans. 
There are situations where I want to implement some logic either prior to the execution of the action method or right after it. In that scenario, the Action Filters are used. Filters are used to determine the logic needed for executing before or after the action method gets executed. Action methods make use of the action filters as an attribute. Different types of MVC action filter are:

1) Action filter (that implements...read more
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