500+ Application Developer Interview Questions and Answers

Abstract classes in Java are classes that cannot be instantiated and are used as blueprints for other classes.

• Abstract classes cannot be instantiated, meaning you cannot create objects of an abstract class.

• Abstract classes can have both abstract and non-abstract methods.

• Interfaces in Java are similar to abstract classes, but they cannot have any method implementations.

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

• Abstract classes can hav...read more

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 @RestController annotation is a specialized version of the @Controller annotation in Spring MVC.

• The @Controller annotation is used to define a controller class in Spring MVC.

• The @RestController annotation is used to define a RESTful web service controller.

• The @RestController annotation is a combination of @Controller and @ResponseBody annotations.

• The @Controller annotation returns a view while the @RestController annotation returns data in JSON or XML format.

• Example: @Con...read more

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

Overloading is when multiple methods have the same name but different parameters. Overriding is when a subclass provides a different implementation of a method inherited from its superclass.

• Overloading allows a class to have multiple methods with the same name but different parameters.

• Overriding occurs when a subclass provides a different implementation of a method inherited from its superclass.

• Overloading is resolved at compile-time based on the method signature.

• Overriding i...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.

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

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 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.

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

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')

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

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

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.

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

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.

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

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.