300+ Interview Questions and Answers

To measure 4L of water using 3L and 5L jars, fill the 5L jar, pour 3L into the 3L jar, empty the 3L jar, and pour the remaining 2L from the 5L jar into the 3L jar. Finally, fill the 5L jar again and pour 1L into the 3L jar. Now, the 5L jar contains 4L of water.

• Fill the 5L jar completely

• Pour 3L from the 5L jar into the 3L jar

• Empty the 3L jar

• Pour the remaining 2L from the 5L jar into the 3L jar

• Fill the 5L jar again

• Pour 1L from the 5L jar into the 3L jar

Singleton class is a class that can only have one instance at a time.

• It is used to control access to a shared resource or limit the instantiation of a class to one object.

• To make a class singleton, make the constructor private and provide a static method to get the instance.

• Example: public class Singleton { private static Singleton instance = new Singleton(); private Singleton() {} public static Singleton getInstance() { return instance; } }

Challenges faced in RPA experience and how resolved

• One challenge was automating a process with multiple decision points, resolved by creating a decision tree

• Another challenge was handling exceptions, resolved by implementing exception handling mechanisms

• Integration with legacy systems was a challenge, resolved by creating custom connectors

• Lack of standardization in input data was a challenge, resolved by implementing data validation and cleansing mechanisms

vptr stands for virtual pointer and vptr table is a table of function pointers used in polymorphism in C++.

• vptr is a hidden member variable in C++ objects that points to the vptr table.

• vptr table is a table of function pointers that maps virtual functions to their addresses.

• Each object of a class with virtual functions has its own vptr and shares the same vptr table with other objects of the same class.

• vptr and vptr table are created when an object of a class with virtual fun...read more

Serialization is the process of converting an object into a stream of bytes, while deserialization is the reverse process.

• Serialization is used for data storage, transmission, and object persistence.

• Deserialization is used to recreate the original object from the serialized data.

• Examples of serialization formats include JSON, XML, and binary formats like Protocol Buffers and Apache Avro.

• Serialization can also be used for deep copying objects.

• Deserialization can be vulnerable ...read more

Program to find duplicate elements in arraylist with minimum iterations

• Use HashSet to store unique elements and ArrayList to store duplicates

• Iterate through the ArrayList only once

• Use contains() method to check if element is already in HashSet

Weigh 3 groups of 3 balls each, then weigh 2 heaviest balls from the heaviest group to find the heaviest ball.

• Divide the 9 balls into 3 groups of 3 balls each.

• Weigh the first 2 groups against each other.

• If one group is heavier, weigh 2 balls from that group against each other to find the heaviest ball.

• If both groups weigh the same, weigh the third group to find the heaviest group.

• Weigh 2 heaviest balls from the heaviest group to find the heaviest ball.

Answering coding questions on string reversal, variable swapping, and pattern printing.

• For string reversal, use a loop to iterate through the string and append each character to a new string in reverse order.

• To separate vowels and consonants, use a loop to iterate through the string and check if each character is a vowel or consonant.

• To swap two variables without a third variable, use arithmetic operations or XOR bitwise operator.

• For pattern printing, use nested loops to prin...read more

Const reference in copy constructor is used to avoid unnecessary object copying and improve performance.

• Const reference allows us to pass objects by reference without modifying them.

• Using const reference in copy constructor avoids creating a temporary copy of the object being passed.

• It helps in preventing unnecessary memory allocation and improves performance.

• Const reference ensures that the original object is not modified during the copy construction process.

Program to display a pattern of numbers in a pyramid shape.

• Use nested loops to print the numbers in the desired pattern.

• The outer loop controls the number of rows and the inner loop prints the numbers in each row.

• Use a variable to keep track of the number to be printed in each row.

• Print a new line after each row is printed.

Swapping of numbers can be done using call by value, address and reference.

• Call by value: Pass the values of variables as arguments to the function. Swap the values inside the function.

• Call by address: Pass the addresses of variables as arguments to the function. Swap the values using pointers inside the function.

• Call by reference: Pass the references of variables as arguments to the function. Swap the values using references inside the function.

Right outer join is a type of join operation that returns all the rows from the right table and the matching rows from the left table.

• Right outer join is denoted by the RIGHT JOIN keyword in SQL.

• It is used to combine rows from two tables based on a related column.

• In the result set, unmatched rows from the right table will have NULL values for the columns of the left table.

• A real-world scenario for using a right outer join is when analyzing customer data and sales data. The ri...read more

Convert string to integer without using inbuilt function

• Iterate through each character and multiply by 10 and add the integer value of the character

• Use ASCII values to convert character to integer

• Handle negative numbers separately

To create a backup table in MySQL, use the CREATE TABLE statement with SELECT INTO.

• Use the CREATE TABLE statement with SELECT INTO to create a backup table.

• Specify the name of the backup table and the name of the original table.

• Use the SELECT INTO statement to copy the data from the original table to the backup table.

• Example: CREATE TABLE backup_table SELECT * FROM original_table;

• Make sure to regularly update the backup table to ensure data consistency.

OOPs concepts include Encapsulation, Inheritance, Abstraction, and Polymorphism.

• Encapsulation: bundling of data and methods that operate on that data

• Inheritance: creating new classes from existing ones

• Abstraction: hiding implementation details and showing only necessary information

• Polymorphism: ability of objects to take on multiple forms or behaviors

CSS position properties are used to position elements on a web page.

• The position property specifies the type of positioning method used for an element.

• The top, bottom, left, and right properties are used to position the element.

• The static, relative, absolute, fixed, and sticky values are used for the position property.

• Static is the default value and elements are positioned according to the normal flow of the page.

• Relative positions the element relative to its normal position....read more

Key concepts of OOP include encapsulation, inheritance, polymorphism, and abstraction.

• Encapsulation: Bundling data and methods that operate on the data into a single unit (object).

• Inheritance: Allowing a class to inherit properties and behavior from another class.

• Polymorphism: Objects of different classes can be treated as objects of a common superclass.

• Abstraction: Hiding complex implementation details and showing only the necessary features to the outside world.

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 the pair will be stored.

• If multiple keys hash to the same index (collision), a linked list is used to store these pairs.

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

A multi-threading program to print 1 2 1 2 using 2 threads.

• Create two threads and pass a flag to each thread to print either 1 or 2.

• Use a synchronization mechanism like mutex or semaphore to ensure alternate printing.

• Join the threads to wait for their completion.

Multithreading is the ability of a CPU to execute multiple threads concurrently. POSIX thread is a standard for thread creation and management.

• Multithreading allows multiple threads to run concurrently, improving performance and responsiveness.

• POSIX thread (pthread) is a standard for creating and managing threads in Unix-based systems.

• Thread synchronization is the coordination of threads to ensure that they do not interfere with each other's execution.

• Mutexes, semaphores, and...read more

SDLC, STLC, Waterfall model, smoke testing, black box testing, quality, stub and driver, levels of testing, UAT, system testing, defect, defect life cycle.

• SDLC (Software Development Life Cycle) is a process followed for software development.

• STLC (Software Testing Life Cycle) is a process followed for software testing.

• Waterfall model is a linear sequential approach to software development.

• Smoke testing is a preliminary test to check if the software is stable enough for further...read more

Garbage collector in Java is an automatic memory management system that frees up memory by removing unused objects.

• Garbage collector runs in the background and identifies objects that are no longer in use

• It frees up memory by removing those unused objects

• It helps prevent memory leaks and improves performance

• Java provides different types of garbage collectors such as Serial, Parallel, CMS, and G1

• Example: If an object is created but not used anymore, the garbage collector will ...read more

Volatile keyword is used to indicate that a variable's value can be changed unexpectedly.

• It is used in multi-threaded programming to ensure that the value of a variable is always up-to-date and consistent across all threads.

• It prevents the compiler from optimizing code that accesses the variable, ensuring that the variable is always read from memory and not from a cache.

• Examples include hardware registers, shared memory, and global variables that can be accessed by multiple t...read more

Interview questions for Automation Test Engineer

• To run failed test case, use failed.xml

• Click can be used via Actions class or JavascriptExecutor

• Array programs: reverse, second highest number

• Constructor in abstract class

• Test plan and scenario definition

• Roles and responsibilities in current organization

• Disable test cases using keyword or include/exclude in suite

• Polymorphism concept

• Unix commands used in day to day activity

• TestNG annotations and keywords

• Code for scroll up and dow...read more

Program to reverse a string in any language

• Create an empty string variable to store the reversed string

• Loop through the original string from the end to the beginning

• Append each character to the empty string variable

• Return the reversed string

Different types of joins in SQL include inner join, left join, right join, and full outer join.

• Inner join: Returns rows when there is a 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 outer join: Returns rows when there is a match in either table.

The best technique to generate automated test report is to use a reporting tool that integrates with the automation framework.

• Choose a reporting tool that supports the programming language and automation framework being used

• Configure the reporting tool to generate reports in the desired format

• Include relevant information in the report such as test case name, status, and duration

• Add screenshots or videos to the report to provide additional context

• Schedule the report to be gene...read more

Recursion is a process in which a function calls itself repeatedly until a base condition is met.

• Recursion involves breaking down a problem into smaller subproblems and solving them recursively.

• It uses a stack to keep track of function calls and their parameters.

• Examples include factorial, Fibonacci sequence, and binary search.

• Compiler executes recursion by allocating memory for each function call and storing the return address and local variables on the stack.

• It then pops th...read more

Views in SQL are virtual tables that display data from one or more tables.

• Views are created using SELECT statements.

• They can be used to simplify complex queries.

• They can also be used to restrict access to sensitive data.

• Views do not store data themselves, but rather display data from other tables.

• Example: CREATE VIEW myView AS SELECT * FROM myTable WHERE column = 'value';

Answers to questions related to PL/SQL concepts like cursor, primary key, unique key, triggers, views, bulk collection, and dynamic queries.

• A cursor is a pointer to a private SQL area that stores information about the processing of a SELECT or DML statement

• Primary key uniquely identifies each record in a table, while a unique key ensures that all values in a column are distinct

• Triggers are stored programs that are fired automatically in response to specific events or changes ...read more

Null pointer points to nothing, while dangling pointer points to memory that has been deallocated.

• Null pointer is a pointer that does not point to any memory location.

• Dangling pointer is a pointer that points to memory that has been deallocated.

• Accessing a null pointer will result in a segmentation fault.

• Accessing a dangling pointer can lead to unpredictable behavior or crashes.

• Example: int* nullPtr = nullptr; int* danglingPtr = new int; delete danglingPtr; danglingPtr = null...read more

My expected CTC would depend on the job role, company size, location, and benefits package.

• Consider the job role and responsibilities when determining expected CTC.

• Research industry standards and average salaries for similar positions.

• Factor in the company size and location, as cost of living varies.

• Take into account additional benefits such as healthcare, retirement plans, and bonuses.

• Be prepared to negotiate based on your skills, experience, and market demand.

Constructor is used to initialize an object while method is used to perform an action on an object.

• Constructor is called automatically when an object is created while method is called explicitly.

• Constructor has the same name as the class while method has a unique name.

• Constructor does not have a return type while method has a return type.

• Example of constructor: public class Car { public Car() { //initialize variables } }

• Example of method: public void startEngine() { //perform...read more

Program to reverse a string in minimum iteration

• Use two pointers, one at the start and one at the end of the string

• Swap the characters at the two pointers and move the pointers towards each other

• Repeat until the pointers meet in the middle of the string