80+ Interview Questions and Answers

To find a line that best fits the data with 1000 samples and 700 dimensions, we can use linear regression.

• For unsupervised ML approach, we can use Principal Component Analysis (PCA) to reduce dimensions and then fit a line using linear regression.

• For supervised ML approach, we need to select a target column. We can choose any of the 700 dimensions as the target and treat it as a regression problem.

• Potential problems of treating this as a supervised problem include: lack of in...read more

Abstract class can have implemented methods while interface cannot.

• Abstract class can have constructors while interface cannot

• Abstract class can have instance variables while interface cannot

• A class can implement multiple interfaces but can only extend one abstract class

• Java 8 introduced default and static methods in interfaces

Tokenization in NLP is the process of breaking down text into smaller units called tokens.

• Tokenization is a fundamental step in NLP for text preprocessing.

• Tokens can be words, phrases, or even individual characters.

• Tokenization helps in preparing text data for further analysis or modeling.

• NLTK tokenizers provide additional functionalities like handling contractions, punctuation, etc.

• str.split() may not handle complex tokenization scenarios as effectively as NLTK tokenizers.

Collection is an interface while Collections is a utility class in Java.

• Collection is an interface that provides a standard way to represent and manipulate a group of objects.

• Collections is a utility class that provides various methods for working with collections.

• Collection is a single entity while Collections is a group of methods.

• Example: List is a type of Collection while Collections.sort() is a method in Collections class.

• Collection is present in java.util package while ...read more

Program to remove duplicate elements from an array of strings.

• Create a new empty array to store unique elements.

• Iterate through the original array and check if each element is already present in the new array.

• If not present, add it to the new array.

• Return the new array with unique elements.

Java 8 introduced several new features including lambda expressions, streams, and default methods.

• Lambda expressions for functional programming

• Streams for efficient processing of large data sets

• Default methods to add new functionality to existing interfaces

• Date and Time API for improved handling of date and time

• Nashorn JavaScript engine for improved performance

• Parallel array sorting for improved performance

• Type annotations for improved code analysis

Yes, static methods can be used in an interface.

• Static methods in an interface can be used to provide utility methods that are not tied to any specific instance of the interface.

• These methods can be called directly on the interface itself, without the need for an instance of a class that implements the interface.

• Static methods in an interface cannot be overridden by implementing classes.

• They can be useful for providing common functionality or helper methods that are related t...read more

Dependency injection is a design pattern used in Spring to inject dependencies into an object.

• Dependency injection is used to reduce coupling between classes.

• It allows for easier testing and maintenance of code.

• Spring provides three types of dependency injection: constructor injection, setter injection, and field injection.

• Constructor injection is the preferred method as it ensures that all required dependencies are provided at object creation.

• Setter injection is used when op...read more

Variables in Java are containers that store data values. Their scope determines where they can be accessed.

• Java has three types of variables: local, instance, and static

• Local variables are declared within a method and can only be accessed within that method

• Instance variables are declared within a class but outside of any method and can be accessed by any method within that class

• Static variables are declared with the static keyword and can be accessed by any method within that...read more

Constructor is a special method used to initialize objects in Java.

• Constructor has the same name as the class name

• It does not have a return type

• It can be overloaded

• It is called automatically when an object is created

• Example: public class Car { public Car() { // constructor code } }

Abstract classes are classes that cannot be instantiated and can have both concrete and abstract methods. Interfaces are contracts that define a set of methods that a class must implement.

• Abstract classes can have instance variables, constructors, and non-abstract methods, while interfaces cannot.

• A class can implement multiple interfaces, but it can only inherit from one abstract class.

• Abstract classes provide a way to share code among related classes, while interfaces define...read more

Polymorphism in Java can be achieved through method overriding and method overloading.

• Method overriding allows a subclass to provide a different implementation of a method that is already defined in its superclass.

• Method overloading allows multiple methods with the same name but different parameters to be defined in a class.

• Polymorphism allows objects of different classes to be treated as objects of a common superclass.

• Example of method overriding: public class Animal { publi...read more

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

Optimizing performance involves identifying bottlenecks and implementing efficient solutions.

• Identify and address any inefficient algorithms or data structures

• Optimize database queries and indexing

• Implement caching mechanisms to reduce redundant computations

• Use profiling tools to identify performance bottlenecks

• Consider parallel processing or asynchronous operations for resource-intensive tasks

Collection is a framework that provides an architecture to store and manipulate a group of objects. StringBuilder and StringBuffer are classes used for manipulating strings, with StringBuffer being thread-safe.

• Collection is a framework in Java used to store and manipulate groups of objects.

• StringBuilder and StringBuffer are classes used for manipulating strings in Java.

• The main difference between StringBuilder and StringBuffer is that StringBuffer is thread-safe while StringB...read more

Method overloading is a feature in Java that allows multiple methods with the same name but different parameters.

• Method overloading is achieved by defining multiple methods with the same name but different parameter types or number of parameters.

• The compiler determines which method to call based on the arguments passed during the method invocation.

• Method overloading improves code readability and reusability.

• Return type alone is not sufficient to differentiate overloaded metho...read more

To route a payment from foreign country to domestic, one can use international wire transfer or online payment platforms.

• International wire transfer can be done through banks or money transfer services

• Online payment platforms like PayPal, TransferWise, or Payoneer can also be used

• Exchange rates and fees should be considered before choosing a method

• Compliance with regulations and documentation requirements is important

Resolve gap on a Physical Standby in Dataguard by identifying the missing archived redo log files and manually copying them over.

• Check the alert log for errors related to missing archived redo log files

• Identify the sequence number of the missing redo log files

• Manually copy the missing archived redo log files from the primary database to the standby database location

• Register the missing redo log files using the ALTER DATABASE REGISTER LOGFILE command

Create and sort an array of strings in descending order

• Create an array of strings

• Use Arrays.sort() method with Collections.reverseOrder() comparator to sort in descending order

To give security to our application, we can implement various measures such as encryption, authentication, authorization, input validation, and regular security audits.

• Implement encryption to protect sensitive data, such as using SSL/TLS for secure communication.

• Use authentication mechanisms like OAuth, JWT, or multi-factor authentication to verify the identity of users.

• Implement authorization to control access to resources based on user roles and permissions.

• Perform input va...read more

Template driven and reactive form example in Angular

• Use Angular's FormsModule and ReactiveFormsModule modules

• Create form controls using ngModel or formControl directives

• Implement form validation using built-in validators or custom validators

• Handle form submission using reactive approach with observables

Program to find min and max in an array of strings

• Convert array elements to integers

• Initialize min and max variables

• Loop through array and compare values

• Return min and max values

Investigate the issue, analyze performance metrics, identify bottlenecks, optimize queries, and implement performance tuning.

• Investigate the issue by analyzing logs, monitoring tools, and gathering information from the client.

• Analyze performance metrics such as CPU usage, memory usage, disk I/O, and query execution times.

• Identify bottlenecks in the database system such as slow queries, inefficient indexing, or hardware limitations.

• Optimize queries by rewriting them, adding in...read more

Create an array of strings and add the array

• Declare an array of strings

• Initialize the array with values

• Use a loop to add the values to the array

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.

Criteria of testing refers to the standards or requirements that must be met during the testing process. Testing strategies are the approaches or methods used to conduct testing effectively.

• Criteria of testing include functional requirements, performance benchmarks, usability standards, and security protocols.

• Testing strategies may involve manual testing, automated testing, regression testing, exploratory testing, and boundary testing.

• Test cases should be designed based on th...read more

I would assess the situation calmly, prioritize tasks, and seek help if needed.

• Assess the critical situation to understand the severity

• Prioritize tasks based on urgency and importance

• Stay calm and focused to make rational decisions

• Seek help from colleagues or experts if necessary

• Create a plan of action to address the critical situation effectively

HashMap allows null values and one null key, while HashTable does not allow null values.

• HashMap allows null values and one null key, while HashTable does not allow null values.

• HashMap is not synchronized, while HashTable is synchronized.

• HashMap is faster than HashTable.

• Example: HashMap map = new HashMap<>(); map.put(null, "value");

• Example: HashTable table = new HashTable<>(); table.put("key", "value");

Program to reverse a string

• Declare a string variable

• Loop through the string from end to start

• Append each character to a new string variable

• Return the new string variable

To read and write data from ExcelSheet, use DataProvider code. Folder structure of framework should be organized. File upload can be done using appropriate methods.

• Use Apache POI library to read and write data from ExcelSheet

• DataProvider annotation in TestNG can be used to provide data to test methods

• Organize framework with folders like src, test, main, resources, etc.

• Use libraries like Selenium or Robot class to upload files

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.sort(list);

A business contingency firm is a company that helps organizations plan for and respond to unexpected events or crises.

• Provides expertise in risk management and disaster recovery planning

• Assists in developing strategies to minimize disruptions to business operations

• Offers support in implementing emergency response protocols

• Examples: Deloitte, PricewaterhouseCoopers, KPMG

Polymorphism is the ability of an object to take on multiple forms.

• Polymorphism allows objects of different classes to be treated as if they are of the same class.

• It can be achieved through method overloading or method overriding.

• Example: A parent class Animal can have multiple child classes like Dog, Cat, etc. and all of them can have their own implementation of the same method like makeSound().

• Polymorphism helps in achieving loose coupling and flexibility in code design.

Exception handling in Java is a mechanism to handle runtime errors and prevent program termination.

• Java provides try, catch, and finally blocks to handle exceptions.

• Checked exceptions must be caught or declared in the method signature.

• Unchecked exceptions do not need to be caught or declared.

• Example: try { // code that may throw exception } catch (Exception e) { // handle exception }

• Example: try { // code that may throw exception } finally { // cleanup code }

In Java, == is used for comparing reference equality, while .equals() is used for comparing object equality.

• == compares memory addresses of two objects

• .equals() compares the actual contents of the objects

• For primitive data types, == compares values, while for objects, it compares references

• Example: String str1 = new String("hello"); String str2 = new String("hello"); str1 == str2 will be false, but str1.equals(str2) will be true

C is a procedural language while Java is an object-oriented language.

• C is compiled while Java is interpreted

• Java has automatic garbage collection while C requires manual memory management

• Java has platform independence while C is platform dependent

• Java has built-in exception handling while C does not

• Java has a larger standard library than C

ISPs are Internet Service Providers that provide internet access to users.

• ISPs offer different types of internet connections such as DSL, cable, fiber, and satellite.

• Some popular ISPs include Comcast, AT&T, Verizon, and Spectrum.

• ISPs may also offer additional services such as email, web hosting, and virtual private networks (VPNs).

Use SQL query to retrieve the salary of an employee.

• Use SELECT statement to retrieve the salary column from the employee table.

• Specify the employee's ID or name in the WHERE clause to filter the results.

• Consider joining the employee table with other tables if necessary.

• Use appropriate functions like SUM, AVG, MAX, MIN if needed.

• Example: SELECT salary FROM employee WHERE employee_id = 123;

Yes, I have knowledge on cloud computing.

• I have experience working with cloud databases like Oracle Cloud Database

• I am familiar with cloud storage solutions like Amazon S3 and Google Cloud Storage

• I have implemented cloud backup and disaster recovery strategies in previous roles

HashMap is non-synchronized and not thread-safe, while HashTable is synchronized and thread-safe.

• HashMap allows null values and one null key, while HashTable does not allow null keys or values.

• HashMap is faster than HashTable as it is non-synchronized, but HashTable is safer for use in multi-threaded environments.

• HashMap is part of the Java Collections Framework, while HashTable is a legacy class.

A comprehensive banking application with features like account management, transactions, loans, and customer support.

• Include features for account creation, management, and transactions

• Implement secure login and authentication methods

• Incorporate loan application and approval processes

• Provide customer support through chat or call center

• Include features for bill payments, fund transfers, and account statements

Yes, I have knowledge on other RDBMS such as MySQL, SQL Server, and PostgreSQL.

• I have experience working with MySQL, including database design and optimization.

• I am familiar with SQL Server and have performed tasks such as backup and recovery.

• I have worked with PostgreSQL and have knowledge of advanced features like partitioning and replication.

To get a particular record in Redis, use the GET command with the key of the record.

• Use the GET command followed by the key of the record to retrieve it from Redis.

• Example: GET myRecordKey

• If the record is stored as a hash, use the HGET command followed by the hash key and field name.

• Example: HGET myHashKey myFieldName

Assets are resources owned by the bank, while liabilities are obligations or debts owed by the bank.

• Assets include cash, loans, investments, and physical property owned by the bank.

• Liabilities include deposits from customers, loans from other banks, and bonds issued by the bank.

• Assets are used to generate revenue for the bank, while liabilities represent the sources of funds for the bank's operations.

The main competency for a business analyst is the ability to analyze data and communicate effectively with stakeholders.

• Analyzing data to identify trends and insights

• Translating business requirements into technical solutions

• Communicating effectively with stakeholders to gather and validate requirements

• Problem-solving and critical thinking skills

• Attention to detail and strong organizational skills

OOPs is a programming paradigm based on the concept of objects that interact with each other to perform tasks.

• OOPs stands for Object-Oriented Programming

• It involves the use of classes, objects, encapsulation, inheritance, and polymorphism

• Classes are blueprints for creating objects

• Objects are instances of classes

• Encapsulation is the process of hiding data and methods within a class

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

• Polymorphism allow...read more

Oops concepts are fundamental to Java programming and include inheritance, polymorphism, encapsulation, and abstraction.

• Inheritance allows a class to inherit properties and methods from a parent class.

• Polymorphism allows objects to take on multiple forms and behave differently based on their context.

• Encapsulation hides the implementation details of a class from other classes.

• Abstraction allows us to focus on the essential features of an object and ignore the rest.

• Examples inc...read more

Reverse a string using popular programming languages

• Use built-in functions like reverse() in Python

• Iterate through the string in reverse order in C++

• Use StringBuilder.reverse() in Java

Exception handling in Java is a mechanism to handle runtime errors and prevent program termination.

• Java provides try-catch blocks to handle exceptions

• Multiple catch blocks can be used to handle different types of exceptions

• Finally block is used to execute code regardless of whether an exception is thrown or not

• Custom exceptions can be created by extending the Exception class

• Checked exceptions must be handled or declared in the method signature

• Unchecked exceptions do not need ...read more

Manual testing is a process of verifying software manually to find defects and bugs. SQL is a programming language used to manage and manipulate relational databases. Joins are used to combine data from two or more tables based on a related column.

• Manual testing involves executing test cases manually without the use of automation tools

• SQL stands for Structured Query Language and is used to manage and manipulate data in relational databases

• Joins are used to combine data from t...read more

Use the length() function to find the length of the given string.

• Use the length() function in programming languages like Java, Python, C++, etc.

• For example, in Java: String str = 'hello'; int length = str.length();

• Make sure to handle edge cases like empty strings or null values.

Union and Union All are SQL operators used to combine the results of two or more SELECT statements. Subquery is a query within a query.

• UNION combines the results of two or more SELECT statements and removes duplicates

• UNION ALL combines the results of two or more SELECT statements and includes duplicates

• Subquery is a query within a query that is used to retrieve data from one or more tables based on a condition

• Subquery can be used in SELECT, INSERT, UPDATE, and DELETE statemen...read more

Joins in SQL are used to combine rows from two or more tables based on a related column between them.

• Joins are used to retrieve data from multiple tables based on a related column

• Types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN

• INNER JOIN returns rows when there is at least one match in both tables

• 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 f...read more

A prime number is a number greater than 1 that can only be divided by 1 and itself.

• Use a loop to check if the number is divisible by any number other than 1 and itself

• Start checking from 2 up to the square root of the number for efficiency

• If the number is only divisible by 1 and itself, it is a prime number

Agile methodology is a project management approach that emphasizes flexibility, collaboration, and incremental progress.

• Focus on delivering working software in short iterations

• Embrace changing requirements throughout the project

• Encourage close collaboration between cross-functional teams

• Regularly reflect on and improve processes through retrospectives

• Examples: Scrum, Kanban, Extreme Programming (XP)

I have experience in network design, implementation, and troubleshooting.

• Designed and implemented LAN and WAN networks for multiple clients

• Configured and maintained network devices such as routers, switches, and firewalls

• Troubleshot network issues and resolved them in a timely manner

• Implemented network security measures to protect against cyber threats

A real time transactional scenario involves a customer making a purchase online and the payment being processed instantly.

• Customer adds items to their online shopping cart

• Customer enters payment information and confirms purchase

• Payment gateway processes the transaction in real time

• Customer receives confirmation of the purchase and the order is fulfilled

Software Development Life Cycle is a process used by software developers to design, develop, test, and deploy software applications.

• SDLC consists of several phases such as planning, analysis, design, implementation, testing, and maintenance.

• Each phase has its own set of activities and deliverables to ensure the successful completion of the project.

• Examples of SDLC models include Waterfall, Agile, and DevOps.

• SDLC helps in improving the quality of software, reducing development...read more

Performance improvement in Java applications involves optimizing code, using efficient data structures, and minimizing resource usage.

• Optimize code by reducing unnecessary loops and improving algorithms

• Use efficient data structures like HashMaps and ArrayLists

• Minimize resource usage by closing connections and releasing memory when not needed

String programs involve manipulating and processing strings in a programming language.

• Use string concatenation to combine two or more strings

• Use string comparison to check if two strings are equal

• Use string slicing to extract a portion of a string

• Use string formatting to insert variables into a string

The N queens problem is a classic problem of placing N chess queens on an N×N chessboard so that no two queens attack each other.

• Create a recursive function to place queens on the board one by one, checking if the current placement is safe

• Use backtracking to backtrack and try different placements if a conflict is found

• Keep track of the valid solutions and return them at the end

Spiral matrix code in Java

• Create a 2D array to represent the matrix

• Use variables to keep track of current position and direction

• Iterate through the matrix in a spiral pattern

Sort a list of students using Java Stream API

• Use the sorted() method to sort the list based on a comparator

• Use the Comparator.comparing() method to specify the sorting criteria

• Use the collect() method to collect the sorted elements back into a list

Use a set to remove duplicates from a string

• Create a set to store unique characters

• Iterate through the string and add each character to the set

• Convert the set back to a string to get the result

Replace characters from string with another character

• Use a loop to iterate through each character in the string

• Check if the character needs to be replaced and replace it with the desired character

• Return the modified string

A final class is a class that cannot be extended or subclassed.

• Final classes are often used to prevent inheritance and ensure that the class cannot be modified or extended.

• Final classes are typically marked with the 'final' keyword in Java.

• Example: 'String' class in Java is a final class, meaning it cannot be extended.

Different types of collections include lists, sets, maps, and queues.

• Lists: Ordered collection of elements, allows duplicates (e.g. ArrayList, LinkedList)

• Sets: Unordered collection of unique elements (e.g. HashSet, TreeSet)

• Maps: Key-value pairs collection, keys are unique (e.g. HashMap, TreeMap)

• Queues: FIFO (First In First Out) collection (e.g. LinkedList, PriorityQueue)

Reverse a given string

• Create an empty string to store the reversed string

• Iterate through the original string from end to start and append each character to the new string

• Return the reversed string

Hashing in Java is a technique used to convert a key into a unique value, allowing for efficient data retrieval.

• Hashing is used to map data to a fixed-size value, typically for faster retrieval in data structures like HashMaps.

• In Java, the hashCode() method is used to generate a hash value for an object.

• Collisions can occur when two different keys produce the same hash value, which can be resolved using techniques like separate chaining or open addressing.

A test bed is a setup or environment where testing is conducted to evaluate the functionality of a system or software.

• Test bed is a controlled environment used for testing software or systems.

• It includes hardware, software, network configurations, and other necessary components.

• Test bed should replicate the production environment as closely as possible.

• It helps in identifying bugs, performance issues, and compatibility problems.

• Examples of test beds include virtual machines, ...read more

HashMap is a data structure that stores key-value pairs and uses hashing to quickly retrieve values based on keys.

• HashMap internally uses an array of linked lists to store key-value pairs.

• When a key-value pair is added, the key is hashed to determine the index in the array where it will be stored.

• If multiple keys hash to the same index, a linked list is used to handle collisions.

• To retrieve a value, the key is hashed again to find the correct index and then the linked list is...read more

Java uses automatic memory management through garbage collection to allocate and deallocate memory.

• Java uses garbage collection to automatically manage memory allocation and deallocation.

• Garbage collection runs in the background to reclaim memory from objects that are no longer in use.

• Java provides the 'finalize()' method to allow objects to perform cleanup before being garbage collected.

Mkdir command is used to create a new directory in a file system.

• Used to create a new directory in a specified location

• Syntax: mkdir [directory_name]

• Can create multiple directories at once using mkdir -p

• Example: mkdir new_directory

Print a star pattern using loops

• Use nested loops to print the desired pattern

• Start with a small pattern and then increase complexity

• Use '*' character to represent the stars

• Example: For a simple pattern, you can use a loop to print '*' in a single line

JPA stands for Java Persistence API, a Java specification for managing relational data in applications.

• JPA is a part of the Java EE framework and provides a set of interfaces and classes for managing relational data in Java applications.

• It allows developers to interact with databases using object-oriented methods, making it easier to work with database entities in Java code.

• JPA supports object-relational mapping (ORM) which maps Java objects to database tables and vice versa....read more

Various payment types used in banking include cash, checks, wire transfers, credit/debit cards, and online/mobile payments.

• Cash: Physical currency used for transactions.

• Checks: Written orders to pay a specific amount from one account to another.

• Wire Transfers: Electronic transfer of funds between banks.

• Credit/Debit Cards: Plastic cards used to make payments.

• Online/Mobile Payments: Transactions made through internet or mobile apps.

Java is a popular programming language used for developing applications and software.

• Java is an object-oriented programming language.

• It is platform-independent, meaning it can run on any device with a Java Virtual Machine (JVM).

• Java is used for developing web applications, mobile apps, and enterprise software.

• Key concepts in Java include classes, objects, inheritance, and polymorphism.

Hashtable is synchronized and thread-safe, while Hashmap is not synchronized.

• Hashtable is synchronized and thread-safe, while Hashmap is not synchronized.

• Hashtable does not allow null keys or values, while Hashmap allows one null key and multiple null values.

• Hashtable is slower than Hashmap due to synchronization.

• Hashmap is preferred for non-thread-safe applications, while Hashtable is used in multi-threaded environments.

Cloud migration techniques involve moving data, applications, and other business elements to a cloud computing environment.

• Assess current infrastructure and applications to determine what can be migrated to the cloud

• Choose the right cloud migration strategy (rehost, refactor, rearchitect, rebuild, or replace)

• Consider factors like security, compliance, cost, and performance during migration

• Use tools like AWS Server Migration Service, Azure Migrate, or Google Cloud Migrate for ...read more

Maintaining the budget in Scrum involves continuous monitoring, prioritization, and communication.

• Regularly review and adjust the budget based on project progress

• Prioritize features and tasks to stay within budget constraints

• Communicate with stakeholders about budget status and any necessary adjustments

• Use tools like burn-down charts to track budget vs actual spending