Opkey Java Developer Interview Questions and Answers

Pen paper test in the college

Q1. Tell me about yourself
Ans. 
Experienced Java Developer with a passion for creating efficient and scalable applications.
• Over 5 years of experience in Java development

• Strong knowledge of object-oriented programming principles

• Proficient in Spring framework and Hibernate

• Experience with RESTful web services and microservices architecture

• Familiar with Agile methodologies and version control systems like Git
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Q2. About Project and puzzle questions from geeks for geeks
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Q1. Introduction about your self
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Q2. About your knowledge
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Basic aptitude, basic math

A group of 10 my topic was technical skills vs soft skills

Q1. Differentiate between Primary key and unique
Ans. 
Primary key uniquely identifies a record in a table, while unique constraint ensures values in a column are unique.
• Primary key is used to uniquely identify each record in a table

• Primary key does not allow NULL values

• Unique constraint ensures that all values in a column are unique

• Unique constraint allows NULL values
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Q2. MySQL commands and questions on them.. then hr questions
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Nuts and bolts game, to output date in a certain format, one SQL query

Q1. Stacks and Queues
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Q2. Linked lists, arrays, and many more basic fundamental Dsa questions.
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Q1. More about your resume projects.
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Q2. Puzzles and reasoning is asked
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Data structure and aptitude

10 mins given for prepare for the problem and after completing the problem (program ) they asked to explain and asked to upgrade the program by reduce time complexity

Q1. Topic given and want to explain
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Q2. Reverse string without buildin funtion and for loop
Ans. 
Reverse a string without using built-in functions or for loops
• Use recursion to reverse the string

• Pass the substring excluding the first character to the recursive function

• Base case: return the character itself if the length of the string is 1

• Concatenate the last character of the string with the result of the recursive call
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Q1. Introduce your self
Ans. 
I am a passionate software developer with experience in Java, Python, and web development.
• Experienced in Java and Python programming languages

• Skilled in web development technologies like HTML, CSS, and JavaScript

• Worked on projects involving database management with SQL
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Q2. Are you ok with agreement
Ans. 
Yes, I am okay with agreement.
• I am comfortable with signing agreements related to software development projects.

• I understand the importance of agreements in protecting both parties involved in a project.

• I am willing to review and negotiate agreements to ensure they are fair and reasonable.
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Q1. Promises in javascript
Ans. 
Promises in JavaScript are objects representing the eventual completion or failure of an asynchronous operation.
• Promises are used to handle asynchronous operations in JavaScript.

• They can be in one of three states: pending, fulfilled, or rejected.

• Promises can be chained using .then() to handle success and .catch() to handle errors.
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C,c++ questions and two coding questions. basic mcq

Q1. Treeset, hashset difference
Ans. 
TreeSet and HashSet are both implementations of the Set interface in Java, but they have some key differences.
• TreeSet is a sorted set that maintains elements in ascending order, while HashSet does not guarantee any specific order.

• TreeSet uses a Red-Black tree data structure for storage, which allows for efficient retrieval of elements in sorted order.

• HashSet uses a hash table for storage, which provides constant-time p...read more
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Q2. Oops concept, dbms, programming questions
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Q3. Set and treeset and hashset
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