SAP 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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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. 
Remove the Kth Node from the End of a Linked List
You are given a singly Linked List with 'N' nodes containing integer data and an integer 'K'. Your task is to delete the Kth node from the end of this Lin...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 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
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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. Can you 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 Problem Statement
You are provided with two sorted linked lists. Your task is to merge them into a single sorted linked list and return the head of the combined linked list.
...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 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 constan...read more
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Q3. What is the difference between the DELETE and TRUNCATE commands 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. 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 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. 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. 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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Arrays and strings - 90 mins

Create Modules, railway reservation system - 60 mins

Q1. Difference between hashmap and hasptable
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Q2. Why typescript over javascript
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Q3. Find the percentage of increace in the quantity of item after making it price 20% extra
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Q4. What is normalization
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Q5. Date and time api available
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30min duration simple questions

Basic array 2 coding questions

Q1. Introduce yorself
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Q2. Explain about final year project
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Q3. Github link for project
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Q4. What is oops in java
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Q5. What is polymorphism explain with examples
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Basic DSA from the hacker rank website

Q1. Basic to medium questions on javascript, nodejs, MySQL joints, html5 tags
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Q1. Real life problems, Use cases
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Q1. Difference between hashset and hashtable
Ans. 
HashSet is an unordered collection of unique elements, while Hashtable is a synchronized collection of key/value pairs.
• HashSet does not allow duplicate elements, while Hashtable does not allow duplicate keys.

• HashSet does not maintain insertion order, while Hashtable does not guarantee any order.

• HashSet allows null values, while Hashtable does not allow null keys or values.
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Q2. Collection vs Collections
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Collection is an interface in Java that represents a group of objects, while Collections is a utility class that contains static methods for operating on collections.
• Collection is an interface in Java that represents a group of objects.

• Collections is a utility class in Java that contains static methods for operating on collections.

• Example: List list = new ArrayList<>(); Collection collection = list;

• Example: Collections
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Q1. SQL query related questions
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Q2. Write a Java program to find the duplicate in Array
Ans. 
Java program to find duplicates in an array of strings
• Create a HashSet to store unique elements

• Iterate through the array and check if element is already in the HashSet

• If element is already in the HashSet, it is a duplicate
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LeetCode , hard questions on dynamic programming, graphs, and more.

DSA, Cn, os, DBMS, ML

Q1. Is relocation a possibility for this position?
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Q2. Senior role is there
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