BOBCARD Ltd. Interview Questions and Answers

Design patterns are reusable solutions to common software design problems.

• Design patterns help in creating flexible, reusable, and maintainable code.

• Examples of design patterns include Singleton, Factory, Observer, and Decorator.

• I have implemented the Singleton pattern in my previous project to ensure only one instance of a class is created.

• I have also used the Factory pattern to create objects without exposing the instantiation logic to the client code.

Clustered index determines physical order of data while non-clustered index creates a separate structure.

• Clustered index determines the physical order of data in a table while non-clustered index creates a separate structure to store the indexed columns.

• A table can have only one clustered index while multiple non-clustered indexes can be created.

• Clustered index is faster for retrieving large amounts of data while non-clustered index is faster for retrieving small amounts of d...read more

Implemented lazy loading in web applications to improve performance by loading content only when needed.

• Implemented lazy loading for images on a website to reduce initial page load time.

• Utilized libraries like Intersection Observer to trigger loading of elements when they come into view.

• Implemented lazy loading for components in a single page application to improve user experience.

SOLID principles are a set of five design principles that help make software designs more understandable, flexible, and maintainable.

• S - Single Responsibility Principle: A class should have only one reason to change.

• O - Open/Closed Principle: Software entities should be open for extension but closed for modification.

• L - Liskov Substitution Principle: Objects of a superclass should be replaceable with objects of its subclasses without affecting the functionality.

• I - Interface ...read more

Singleton pattern ensures a class has only one instance and provides a global point of access to it.

• Used to restrict instantiation of a class to one object

• Commonly used in logging, driver objects, caching, thread pools, etc.

• Implemented by creating a static method to return the same instance each time

Tree map algorithm problem

• Tree map is a data structure that stores key-value pairs in a sorted order

• The algorithm involves inserting, deleting, and searching for elements in the tree map

• Common operations include finding the minimum and maximum values, and iterating over the elements

• Examples of tree map implementations include Java's TreeMap and C++'s std::map

Prototype pattern is a creational design pattern that allows cloning of objects.

• Used to create new objects by copying an existing object

• Avoids the need for subclassing to create new objects

• Can be implemented using shallow or deep copy methods