Addepar Senior Java Developer Interview Questions and Answers

Q1. Kth node from behind for linked list
Ans. 
Find the Kth node from the end of a linked list
• Traverse the linked list to find the length of the list

• Calculate the position of the Kth node from the beginning

• Traverse the list again to find the Kth node from the end
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Q1. Java 8 Features
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Q2. Reflection API ?
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Q1. Basic Java and SQL query
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General Question depended on daily life

List of employees and get employee name who is getting bonus more the 10000

Q1. Java OPPPS concept
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Q2. String and feature
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Q3. Spring feature and implementation
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Q4. Hibernate and its implementation
Ans. 
Hibernate is a popular Java ORM framework that simplifies database interactions by mapping Java objects to database tables.
• Hibernate is an ORM (Object-Relational Mapping) framework that allows developers to map Java objects to database tables and vice versa.

• It provides a way to perform database operations using Java objects without writing complex SQL queries.

• Hibernate handles the mapping of Java classes to database ta...read more
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Round duration - 60 Minutes
Round difficulty - Medium

This round had 2 questions of DSA where I was asked to first explain my approach and then code it as well in a production ready manner . After that , I was asked some questions related to Operating Systems and Java .

Q1. Delete Kth node From End
You have been given a singly Linked List of 'N' nodes with integer data and an integer 'K'. Your task is to remove the Kth node from the end of the given Linked Lis...read more
Ans. 
Approach : 
1) Maintain two pointers – reference pointer and main pointer. 
2) Initialize both reference and main pointers to head. 
3) First, move the reference pointer to n nodes from head.
4) Now move both pointers one by one until the reference pointer reaches the end. 
5) Now the main pointer will point to nth node from the end. 
6) Return the main pointer.

TC : O(N) where N=length of the Linked
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Q2. Intersection of Linked List
You are given two Singly Linked List of integers, which are merging at some node of a third linked list.
Your task is to find the data of the node at which merging starts. If ...read more
Ans. 
Approach :

I) Using Hashing :

Basically, we need to find a common node of two linked lists. So we hash all nodes of the first list and then check the second list.

Note : Hash the nodes not the node value

1) Create an empty hash set.
2) Traverse the first linked list and insert all nodes' addresses in the hash set.
3) Traverse the second list. For every node check if it is present in the hash set. If we find a node in the has...read more
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Q3. OS Question
Explain the Life Cycle of a Thread in Java .
Ans. 
In Java, a thread always exists in any one of the following states. These states are:

1) New
2) Active
3) Blocked / Waiting
4) Timed Waiting
5) Terminated

Explanation of Different Thread States : 

1) New: Whenever a new thread is created, it is always in the new state. For a thread in the new state, the code has not been run yet and thus has not begun its execution.

2) Active: When a thread invokes the start() method, it ...read more
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Round duration - 60 Minutes
Round difficulty - Medium

This round also had 2 questions of DS/Algo where I coded one of them and then we switched our discussion to DBMS and OOPS ( particularly in Java ) .

Q1. Merge Two Sorted Linked Lists
You are given two sorted linked lists. You have to merge them to produce a combined sorted linked list. You need to return the head of the final linked list.
Note:
The give...read more
Ans. 
Approach 1 (Recursive) :

1) Compare the head of both linked lists.
2) Find the smaller node among the two head nodes. The current element will be the smaller node among two head nodes.
3) The rest elements of both lists will appear after that.
4) Now run a recursive function with parameters, the next node of the smaller element, and the other head.
5) The recursive function will return the next smaller element linked with r...read more
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Q2. LRU Cache Implementation
Design and implement a data structure for Least Recently Used (LRU) cache to support the foll...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 constan...read more
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Q3. DBMS Question
Difference between the DELETE and TRUNCATE command in DBMS.
Ans. 
Answer :

DELETE command:

1) This command is needed to delete rows from a table based on the condition provided by the WHERE clause.
2) It can be rolled back if required.
3) It maintains a log to lock the row of the table before deleting it and hence it’s slow.

TRUNCATE command:
1) This command is needed to remove complete data from a table in a database. It is like a DELETE command which has no WHERE clause.
2) It removes com...read more
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Q4. OOPS Question
What is 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 re...read more
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Round duration - 50 Minutes
Round difficulty - Medium

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

Q1. System Design Question
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 in...read more
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Q2. OS Question
Why Java is platform independent and JVM 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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Common simple codings on String Manipulation.

Q1. Deep questions on Basics.
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Q1. Walk through your Resume
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