Startup Software Developer Interview Questions and Answers for Experienced

Weak reference is a reference that does not prevent the object from being garbage collected.

• Weak references are used to refer to objects that can be garbage collected if there are no strong references to them.

• They are typically used in scenarios where you want to hold a reference to an object, but don't want to prevent it from being collected.

• Weak references are implemented using weak reference queues, which allow you ...read more

Singleton pattern ensures a class has only one instance, while allowing global access to it.

• Implement a private constructor to prevent direct instantiation.

• Create a static method to provide a single point of access to the instance.

• Use lazy initialization to create the instance only when needed.

• Ensure thread safety in a multithreaded environment using synchronization or double-checked locking.

• Breaking the singleton patt...read more

Annotations used in Spring Framework for defining components and services.

• Annotations like @Component, @Service, and @Controller are used for defining components in Spring Framework.

• @RestController is used for defining RESTful web services.

• @Configuration is used for defining configuration classes.

• @Transactional is used for defining transactional methods.

• All these annotations help in defining and managing dependencies i

HashSet is implemented using a HashMap internally. Same hashcode is generated when two objects have the same value for hashCode() and equals() methods.

• HashSet internally uses a HashMap to store its elements.

• The hashcode of an object is generated using the hashCode() method.

• If two objects have the same value for hashCode() and equals() methods, they will generate the same hashcode.

• For example, if two String objects have...read more

SQL Cursor is a database object used to manipulate data row by row.

• Cursor is used to fetch and process data row by row

• Index is a database object used to speed up data retrieval

• Aggregate functions are used to perform calculations on a set of values

• Examples of aggregate functions are SUM, AVG, COUNT, MAX, MIN

Generate palindrome string with given length and distinct characters.

• Create a char array of length n and fill it with distinct characters.

• Loop through the array and add the characters in reverse order to create a palindrome.

• Repeat the process until the required number of palindromes are generated.

• If k is less than the length of the palindrome, use the first k distinct characters.

Find the highest value that occurs the same number of times within an array.

• Iterate through the array and count the occurrences of each value.

• Store the counts in a dictionary or hash map.

• Find the maximum count and check which value(s) have that count.

• Return the highest value among those with the maximum count.

Count occurrences of a character in a string and output in a specific format.

• Use a hash table to store the count of each character.

• Loop through the string and update the count in the hash table.

• Create the output string using the hash table.

Converts a string from Camel case to Snake case.

• Loop through the string and check for uppercase letters

• Insert an underscore before each uppercase letter

• Convert the string to lowercase

Logic to get Map using Stream API to show balance of each person

• Use Stream API to group accounts by name

• Use map() to get the sum of balances for each group

• Collect the results into a Map

To check palindrome and anagram of a string with O(n), use a hash table to store character frequencies.

• Create a hash table to store the frequency of each character in the string.

• For palindrome, check that no more than one character has an odd frequency.

• For anagram, compare the hash tables of the two strings.

• If the hash tables are equal, the strings are anagrams.

• If the hash tables differ by only one character, the strin...read more

Optimized solutions and core principles applied in OOPS

• Encapsulation, Inheritance, Polymorphism, Abstraction are core principles of OOPS

• Optimized solutions can be achieved through efficient algorithms and data structures

• Design patterns like Singleton, Factory, Observer can also be used for optimized solutions

Yes, the string class can be extended in most programming languages.

• Inheritance can be used to extend the functionality of the string class.

• By creating a new class that inherits from the string class, additional methods and properties can be added.

• Extending the string class allows for customization and adding specific functionality to strings.

• Example: In Python, the string class can be extended by creating a new class

Implicit objects in JSP are predefined objects that are available for use without any declaration or initialization.

• Implicit objects in JSP include request, response, session, application, out, config, pageContext, page, exception, and others.

• These objects provide access to various aspects of the JSP environment and can be used to perform common tasks.

• For example, the request object allows access to HTTP request parame...read more

A hash map is a data structure that uses a hash function to map keys to values.

• Hash map stores key-value pairs

• It uses a hash function to compute an index for each key

• Collisions can occur when two keys hash to the same index

• Hash maps provide fast access to values based on their keys

StringBuffer and StringBuilder are both used to manipulate strings, but StringBuffer is thread-safe while StringBuilder is not.

• StringBuffer is synchronized, making it safe for use in multi-threaded environments.

• StringBuilder is not synchronized, making it faster but not thread-safe.

• StringBuffer is preferred when multiple threads are involved, while StringBuilder is preferred for single-threaded scenarios.

• Both classes p...read more

MVC is a software architectural pattern that separates an application into three main components: Model, View, and Controller.

• Model represents the data and business logic of the application.

• View is responsible for displaying the user interface.

• Controller handles user input, updates the model, and interacts with the view.

• MVC promotes separation of concerns and modularity in software development.

• Example: In a web applica...read more

Annotations used in RESTful web services

• 1. @Path - Specifies the URI path for the resource

• 2. @GET - Specifies that the method handles HTTP GET requests

• 3. @POST - Specifies that the method handles HTTP POST requests

• 4. @PUT - Specifies that the method handles HTTP PUT requests

• 5. @DELETE - Specifies that the method handles HTTP DELETE requests

• 6. @PathParam - Binds the value of a URI template parameter to a method paramete...read more