Xyz Company Java Developer Interview Questions and Answers for Freshers

DP graphs strings it was good

Q1. Reverse a linkded list
Ans. 
Reverse a linked list by changing the direction of pointers
• Start with three pointers: current, previous, and next

• Iterate through the list, updating pointers to reverse the direction

• Return the new head of the reversed list
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Q2. Print fibonacci series
Ans. 
The Fibonacci series is a sequence of numbers where each number is the sum of the two preceding ones.
• Start with two variables initialized to 0 and 1

• Loop through desired number of iterations, adding the previous two numbers to get the next number

• Print or store each number in the series
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Hackerrank - Hackerrank test including multiple choice and 2 programming questions

Q1. Garbage collector internal implementation algorithm
Ans. 
Garbage collector is an automatic memory management system in Java that reclaims memory by deallocating objects no longer in use.
• Garbage collector uses different algorithms like Mark-Sweep, Mark-Compact, and Copying to reclaim memory.

• Mark-Sweep algorithm marks objects as reachable or unreachable, then sweeps through and deletes the unreachable objects.

• Mark-Compact algorithm moves reachable objects to one end of the mem...read more
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It was just a typical logical reasoning and aptitude MCQ test

There were 2 coding questions and you can select any language for solving it. The test was online

Q1. He simply asked me which coding language I prefer and why ? (Mine was C++)
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Q2. Difference between C and C++?
Ans. 
C is a procedural programming language while C++ is an object-oriented programming language.
• C is a procedural programming language, while C++ supports both procedural and object-oriented programming.

• C does not have classes and objects, while C++ does.

• C does not support function overloading, while C++ does.

• C does not have exception handling, while C++ does.

• C does not have namespaces, while C++ does.
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Q3. What is Object oriented programming?
Ans. 
Object oriented programming is a programming paradigm based on the concept of objects, which can contain data and code.
• Objects are instances of classes, which define the structure and behavior of the objects.

• Encapsulation, inheritance, and polymorphism are key principles of object oriented programming.

• Example: Inheritance allows a class to inherit properties and methods from another class.

• Example: Encapsulation hides t...read more
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Q4. What are the 4 pillars of OOPs?
Ans. 
Encapsulation, Inheritance, Polymorphism, Abstraction
• Encapsulation: Bundling data and methods that operate on the data into a single unit

• Inheritance: Ability of a class to inherit properties and behavior from another class

• Polymorphism: Ability to present the same interface for different data types

• Abstraction: Hiding the complex implementation details and showing only the necessary features
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Q5. Write down code implementing all 4 pillars of OOPs.
Ans. 
Code implementing all 4 pillars of OOPs
• Encapsulation: Encapsulate data within classes and provide public methods to access and modify the data.

• Inheritance: Create a hierarchy of classes where child classes inherit attributes and methods from parent classes.

• Polymorphism: Allow objects of different classes to be treated as objects of a common superclass through method overriding and overloading.

• Abstraction: Hide complex ...read more
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Q6. Difference between Stacks and Queues?
Ans. 
Stacks are Last In First Out (LIFO) data structures, while Queues are First In First Out (FIFO) data structures.
• Stacks: Elements are added and removed from the same end, like a stack of plates. Example: Undo feature in text editors.

• Queues: Elements are added at the rear and removed from the front, like a line of people waiting. Example: Print queue in a printer.
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Q7. Write a code to find the 2nd largest element in an array.
Ans. 
Code to find the 2nd largest element in an array
• Sort the array in descending order and return the element at index 1

• Iterate through the array and keep track of the two largest elements

• Handle edge cases like arrays with less than 2 elements
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Q8. What is merge sort and its Algorithm ?
Ans. 
Merge sort is a divide and conquer algorithm that divides the input array into two halves, sorts them recursively, and then merges them.
• Divide the input array into two halves

• Recursively sort each half

• Merge the sorted halves back together
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Q9. What is DBMS and RDBMS and difference between them?
Ans. 
DBMS stands for Database Management System, while RDBMS stands for Relational Database Management System. RDBMS is a type of DBMS.
• DBMS is a software system that allows users to define, create, maintain and control access to the database.

• RDBMS is a type of DBMS that stores data in a structured format using tables with rows and columns.

• RDBMS enforces a set of rules called ACID properties to ensure data integrity, while D...read more
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Q10. What is SQL and who its different from mySQL?
Ans. 
SQL is a standard language for managing databases, while MySQL is a specific open-source relational database management system.
• SQL stands for Structured Query Language and is used to communicate with databases.

• SQL is a standard language that can be used with various database management systems.

• MySQL is a specific open-source relational database management system that uses SQL.

• MySQL is one of the most popular database m...read more
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Q11. Difference between Delete, Truncate and Drop?
Ans. 
Delete removes specific rows from a table, Truncate removes all rows from a table, and Drop removes the table itself.
• Delete is a DML command that removes specific rows from a table based on a condition.

• Truncate is a DDL command that removes all rows from a table but keeps the table structure.

• Drop is a DDL command that removes the entire table along with its structure.
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Q12. Different kind of Joins in DBMS ?
Ans. 
Different types of joins in DBMS include inner join, outer join, left join, right join, and full join.
• Inner join: Returns rows when there is a match in both tables.

• Outer join: Returns all rows from one table and only matching rows from the other table.

• Left join: Returns all rows from the left table and the matched rows from the right table.

• Right join: Returns all rows from the right table and the matched rows from the ...read more
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Q13. And at last 2 to 3 SQL queries. They were not that hard, Just basic queries.
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2 hours with 4 questions

Q1. Basic oops, os, and two dsa questions, one was on tree and other on priority queue
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First round was an API challenge in which we need to submit our names Reg No. and other details by using an API provided by the company .

Then the second round was coding round in which there were 19 coding multiple choice questions and 2 coding questions based on the profile we applied for . It was 1 hour and 15 mins long test

Q1. The interviewer asked me to intruduce myself and explain the projects on my profile . Then he asked me to few basic questions about Javascript and few coding questions and asked me write psuedo code for th...read more
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Q1. Hr Asked me to intruduce myself and asked me to tell 5 things that arent on my resume , Then she further asked me if i am willing to relocate .She asked me if i am okay with working on diffrent domains if...read more
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Round duration - 90 minutes
Round difficulty - Medium

Q1. Maximum Sum With Specific Difference
You are given an array of integers and a number ‘K’. You can pair two elements in the array 'ARR' if the absolute difference between them is strictly less than ...read more
Ans. Sorting
Approach: We sort the given array in increasing order. For every element, we try to pair it with its previous element first. Since the array is sorted, the value of ‘ARR[i]’ would be more than ‘ARR[i - 1]’. We need to pair with a difference less than ‘K’, which means if 'ARR[i - 2]' can be paired, then ‘ARR[i - 1]’ can also be paired in a sorted array. Here, we prefer the previous element so that if ‘ARR[i]’ - ‘...read more
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Q2. Ninja And The Tree
Ninja is learning tree data structure these days. While learning, she came across learn about the Binary Search tree. She found BST quite interesting. She decided to make her own Binary ...read more
Ans. Brute Force Approach
Algorithm:
 
1. We will initialize an array of integers to store the inorder traversal of the given BST.
2. As two nodes are swapped currently, so the inorder traversal will not be sorted.
3. Sort the array.
4. Now, this is a sorted array so this will represent the inorder traversal of the BST.
5. Insert the array elements back to the tree inorder manner.
Space Complexity: O(n)Explanation:
O(N), where ‘N’ is the num...read more
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