500+ Application Developer Interview Questions and Answers

Clustered index physically reorders the data in the table, while non-clustered index does not.

• Clustered index determines the physical order of data in the table, while non-clustered index does not.

• A table can have only one clustered index, but multiple non-clustered indexes.

• Clustered index is faster for retrieval of data, as it directly points to the actual data rows.

• Non-clustered index is faster for retrieval of specific data, as it points to a separate list of pointers to t...read more

The gold rate has been fluctuating in the past week.

• Gold rate increased on Monday and Tuesday, but decreased on Wednesday and Thursday.

• On Friday, the rate remained stable.

• Overall, there has been a slight decrease in the gold rate over the past week.

HashSet is a collection of unique elements, while HashMap is a key-value pair collection.

• HashSet does not allow duplicate elements, while HashMap allows duplicate values but not duplicate keys.

• HashSet uses a hash table to store elements, while HashMap uses key-value pairs to store data.

• Example: HashSet<String> set = new HashSet<>(); HashMap<String, Integer> map = new HashMap<>();

The code inserts two numbers in a text file, ensuring that the second number is greater than the first and there is no overlap between entries.

• Read the existing entries from the text file

• Check if the new numbers satisfy the conditions

• If conditions are met, insert the new numbers into the file

• Otherwise, display an error message

The @SpringBootApplication annotation is used to mark the main class of a Spring Boot application.

• Combines @Configuration, @EnableAutoConfiguration, and @ComponentScan annotations

• Enables the application to start with a main method

• Automatically scans for Spring components in the package and sub-packages

Adding a new feature using SOLID principles

• Identify the new feature and its requirements

• Analyze the existing codebase and identify areas that need modification

• Apply SOLID principles to design the new feature

• Implement the feature using clean code practices

• Test the feature thoroughly to ensure it meets the requirements

To get distinct data without using distinct keyword, use GROUP BY clause.

• Use GROUP BY clause with the column name to group the data by that column.

• Use aggregate functions like COUNT, SUM, AVG, etc. to get the desired result.

• Example: SELECT column_name FROM table_name GROUP BY column_name;

• Example: SELECT column_name, COUNT(*) FROM table_name GROUP BY column_name;

Dynamic allocation of memory to 2D array is done using double pointer and malloc function.

• Declare a double pointer to hold the 2D array.

• Allocate memory to the first dimension using malloc function.

• Allocate memory to the second dimension using a loop and malloc function.

• Free the memory after use to avoid memory leaks.

• Example: int **arr; arr = (int **)malloc(rows * sizeof(int *));

• Example: for(int i=0; i

Stack is LIFO and Queue is FIFO data structure. Stack is like a stack of plates and Queue is like a queue of people.

• Stack is Last In First Out (LIFO) and Queue is First In First Out (FIFO)

• Stack is like a stack of plates where the last plate added is the first one to be removed

• Queue is like a queue of people where the first person to enter is the first one to leave

• Stack is used in undo-redo functionality in text editors

• Queue is used in printing jobs in a printer

ConcurrentHashMap is a thread-safe implementation of the Map interface in Java.

• ConcurrentHashMap allows multiple threads to read and write to the map concurrently without causing any inconsistencies.

• It achieves thread-safety by dividing the map into segments, each of which can be locked independently.

• ConcurrentHashMap uses a technique called lock striping to minimize contention and improve performance.

• It does not throw ConcurrentModificationException during iteration as it wo...read more

The major difference between 32-bit and 64-bit processors is the amount of memory they can access and process.

• 32-bit processors can access up to 4GB of RAM, while 64-bit processors can access much more, typically 16 exabytes (16 billion GB) of RAM.

• 64-bit processors can handle larger chunks of data at once, leading to improved performance in tasks that require intensive calculations or large datasets.

• Software designed for 64-bit processors may not be compatible with 32-bit pro...read more

Multitasking involves executing multiple tasks simultaneously, while multiprogramming involves running multiple programs on a single processor.

• Multitasking allows multiple tasks to run concurrently, switching between them quickly.

• Multiprogramming involves loading multiple programs into memory and executing them concurrently.

• Examples of multitasking include running multiple applications on a computer or a smartphone.

• Examples of multiprogramming include running multiple instanc...read more

Mutex is used for exclusive access to a resource, while semaphore is used for controlling access to a resource by multiple threads.

• Mutex is binary and allows only one thread to access the resource at a time.

• Semaphore can have a count greater than one, allowing multiple threads to access the resource simultaneously.

• Mutex is used for protecting critical sections of code, while semaphore is used for synchronization between threads.

• Example: Mutex is like a key to a room that only...read more

I have knowledge on various devops tools and have worked on challenging use cases such as implementing continuous integration and deployment pipelines using Jenkins and Docker.

• Proficient in using Jenkins, Docker, Git, Ansible, and Kubernetes

• Implemented CI/CD pipelines for multiple projects

• Automated deployment process using Ansible and Kubernetes

• Implemented containerization using Docker and Kubernetes

• Implemented infrastructure as code using Terraform

• Challenging use case: Setti...read more

Undo operation (ctrl + z) is implemented by maintaining a stack of previous states.

• When a change is made, the current state is pushed onto the stack

• When undo is called, the top state is popped and applied

• Redo is implemented by maintaining a stack of undone states

• Some applications may also implement a limit on the number of undo/redo steps

• Undo/redo can be implemented at different levels (e.g. character, word, paragraph)

Creating a pointer for an abstract class and pointing it to a derived class object with a function name conflict.

• Use virtual keyword for the function in the abstract class.

• Use override keyword for the function in the derived class.

• Access the function using the pointer with the derived class object.

UNION removes duplicates while UNION ALL does not

• UNION combines result sets and removes duplicates

• UNION ALL combines result sets without removing duplicates

• UNION is slower than UNION ALL as it involves removing duplicates

• Use UNION when you want to remove duplicates, use UNION ALL when duplicates are acceptable

You can measure 4 liters by following these steps:

• Fill the 5 liters container completely

• Pour the 5 liters into the 3 liters container, leaving 2 liters in the 5 liters container

• Empty the 3 liters container

• Pour the remaining 2 liters from the 5 liters container into the 3 liters container

• Fill the 5 liters container again

• Pour 1 liter from the 5 liters container into the 3 liters container, which now has 3 liters

• The 5 liters container now has 4 liters

Regular expression for 10-digit numeric characters starting with 1, 2, or 3.

• Use the pattern ^[1-3]\d{9}$ to match the criteria

• The ^ symbol denotes the start of the string

• The [1-3] specifies that the first digit must be 1, 2, or 3

• \d{9} matches exactly 9 numeric digits

• $ indicates the end of the string

Data encapsulation is the concept of bundling data with the methods that operate on that data within a class.

• Data encapsulation restricts access to certain components of an object, protecting the data from external interference.

• It allows for better control over the data by hiding the implementation details and only exposing necessary information through methods.

• Encapsulation helps in achieving data abstraction, where the internal representation of an object is hidden from the...read more

Varying parameters can be passed using arrays of strings in COBOL to stored procedures.

• Define an array in COBOL to hold the parameters

• Populate the array with the varying parameters

• Pass the array as a parameter to the stored procedure

• In the stored procedure, use the array to access the varying parameters

Software development life cycle (SDLC) is a process followed to develop software. Testing is done to ensure quality and functionality.

• SDLC is a process that includes planning, designing, coding, testing, and maintenance.

• Testing is done to identify and fix defects, ensure functionality, and improve quality.

• Types of testing include unit testing, integration testing, system testing, and acceptance testing.

• Testing can be manual or automated, and should be done throughout the SDLC...read more

To find the middle element of a linked list in a single traversal.

• Use two pointers, one moving at twice the speed of the other.

• When the faster pointer reaches the end, the slower pointer will be at the middle.

• If the linked list has even number of elements, the middle will be the second of the two middle elements.

The algorithm for the upcoming semester project involves developing an application.

• Identify the requirements and objectives of the project

• Design the application architecture and user interface

• Implement the necessary algorithms and data structures

• Test and debug the application

• Optimize the performance and efficiency of the code

• Document the project for future reference

A join in SQL is used to combine rows from two or more tables based on a related column between them.

• 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 from the left table.

• FULL JOIN returns rows when there is a match in one of t...read more

When a parent process is terminated, the child process becomes an orphan and is adopted by the init process.

• When a parent process is terminated, the child process is not automatically terminated.

• The child process becomes an orphan and is adopted by the init process.

• The init process becomes the new parent of the orphaned child process.

• The orphaned child process continues to run independently until it completes or is terminated.

Incode refers to the code that is embedded within a program. Deadlock recovery is the process of resolving deadlocks in a system. Hierarchical file structure is a way of organizing files in a hierarchical manner.

• Incode refers to the code that is written within a program.

• Deadlock recovery involves detecting and resolving deadlocks in a system.

• Hierarchical file structure organizes files in a tree-like structure with parent and child relationships.

• Example of incode: Inline funct...read more

Hibernate get() returns object by id, load() returns proxy object until accessed.

• get() method returns the object from the database by its id.

• load() method returns a proxy object until it is accessed, then it loads the object from the database.

• get() method returns null if the object is not found in the database, while load() method throws an exception.

• get() method is eager loading, while load() method is lazy loading.

Data from an Excel sheet can be brought into Databricks using the read method in Databricks.

• Use the read method in Databricks to read the Excel file.

• Specify the file path and format (e.g. 'xlsx') when using the read method.

• Transform the data as needed using Databricks functions and libraries.

• Example: df = spark.read.format('com.crealytics.spark.excel').option('useHeader', 'true').load('file.xlsx')

Types of search include linear search, binary search, and hash table search. They are used in real life for finding information efficiently.

• Linear search: sequentially checks each element in a list until a match is found.

• Binary search: divides a sorted array in half to quickly find the target value.

• Hash table search: uses a hash function to map keys to values for fast retrieval.

• Real life example: Using linear search to find a specific book in a library.

• Real life example: Usin...read more

The code prints the transpose of a given matrix.

• Iterate through each row and column of the matrix.

• Swap the elements at the current row and column with the elements at the current column and row.

• Print the transposed matrix.

Code to count the number of times '1' occurs from 1 to 999999

• Loop through all numbers from 1 to 999999

• Convert each number to a string and count the number of '1's in it

• Add the count to a running total

• Return the total count

Code to find the middle element of a linked list

• Traverse the linked list with two pointers, one moving twice as fast as the other

• When the fast pointer reaches the end, the slow pointer will be at the middle element

• If the linked list has even number of elements, return the second middle element

No, static methods cannot be overridden in Java.

• Static methods belong to the class itself, not to any specific instance of the class.

• Subclasses can define static methods with the same signature as the parent class, but it is not considered overriding.

• Example: Parent class has a static method 'display()', and subclass also has a static method 'display()'. These are two separate methods, not overriding each other.

Find the repeating number in an array.

• Iterate through the array and store each element in a hash table or set.

• If an element is already present in the hash table, it is a repeating number.

• Alternatively, sort the array and check for adjacent elements with the same value.

• Time complexity: O(n) or O(nlogn) depending on the approach used.

Virtual functions in C++ allow a function to be overridden in a derived class, enabling polymorphic behavior.

• Virtual functions are declared in a base class with the 'virtual' keyword.

• They are overridden in derived classes to provide specific implementations.

• Virtual functions enable polymorphism, allowing objects of different derived classes to be treated as objects of the base class.

• Example: class Shape { virtual void draw() { ... } }; class Circle : public Shape { void draw(...read more

Infinite loop can occur due to logical errors in the loop condition or the loop body.

• Incorrect loop condition

• Missing or incorrect loop termination condition

• Infinite recursion

• Deadlock or race condition

• Hardware or software failure

Agile methodologies are preferred for their flexibility, collaboration, and ability to adapt to changing requirements.

• Agile methodologies prioritize individuals and interactions over processes and tools.

• They emphasize working software over comprehensive documentation.

• Agile allows for frequent iterations and feedback, leading to quicker delivery of value to customers.

• Scrum, Kanban, and Extreme Programming (XP) are popular agile frameworks.

• Agile promotes continuous improvement ...read more

DELETE removes specific rows from a table, while TRUNCATE removes all rows and resets auto-increment values.

• DELETE is a DML command, while TRUNCATE is a DDL command.

• DELETE can be rolled back, while TRUNCATE cannot be rolled back.

• DELETE triggers ON DELETE triggers, while TRUNCATE does not trigger any triggers.

• DELETE is slower as it logs individual row deletions, while TRUNCATE is faster as it logs the deallocation of the data pages.

• Example: DELETE FROM table_name WHERE conditi...read more

Find the common ancestor of two given nodes in a tree

• Traverse the tree from the root node

• Check if both nodes are on the same side of the current node

• If not, return the current node as the common ancestor

• If yes, continue traversing down that side of the tree

To find the second largest number in an array using JavaScript, sort the array in descending order and return the element at index 1.

• Sort the array in descending order using the sort() method.

• Access the element at index 1 to get the second largest number.

Python is a versatile and powerful programming language known for its simplicity and readability.

• Python has a simple and easy-to-understand syntax, making it beginner-friendly.

• It has a large standard library with built-in modules for various tasks, reducing the need for external dependencies.

• Python supports multiple programming paradigms, including procedural, object-oriented, and functional programming.

• It has excellent community support with a vast number of libraries and fr...read more

Arrange 4 coins to make maximum number of triangles

• Place 3 coins in a triangle formation and the fourth coin in the center to form 4 triangles

• Place 2 coins on top of each other and the other 2 coins on either side to form 2 triangles

• Place 2 coins in a line and the other 2 coins on either side to form 2 triangles

The time complexity of 8 queens algorithm is O(n!).

• The algorithm checks all possible permutations of the queens on the board.

• The number of permutations is n! where n is the number of queens.

• For 8 queens, there are 8! = 40,320 possible permutations.

• The algorithm has to check each permutation to find a valid solution.

• Therefore, the time complexity is O(n!).

Decode function is used in PL/SQL to conditionally return a value based on specified conditions.

• Decode function compares an expression with a series of search values and returns a result when a match is found.

• It is commonly used to replace multiple IF-THEN-ELSE statements.

• Syntax: DECODE(expression, search_value1, result1, search_value2, result2, ..., default_result)

• Example: DECODE(salary, 1000, 'Low', 2000, 'Medium', 'High') returns 'Low' if salary is 1000, 'Medium' if 2000, ...read more

Procedures and functions are both subprograms in programming languages, but they differ in their return values.

• Procedures do not return a value, while functions do.

• Procedures are used to perform actions or tasks, while functions are used to calculate and return a value.

• Functions can be used in expressions, while procedures cannot.

• Functions have a return statement, while procedures do not necessarily have one.

• Procedures can have output parameters to return values, while functi...read more

I prioritize tasks by importance and deadline, using tools like to-do lists and calendars to manage time efficiently.

• Create a to-do list with tasks ranked by importance and deadline

• Use a calendar to schedule time for each task

• Break down larger tasks into smaller, manageable chunks

• Eliminate distractions and focus on one task at a time

• Regularly review and adjust priorities as needed