Alibaba Group Regional Sales Manager Interview Questions and Answers

An immutable class is a class whose instances cannot be modified after creation.

• Make all fields private and final

• Don't provide any setter methods

• Ensure that any mutable objects passed to the constructor are defensively copied

• Make the class final so that it cannot be subclassed

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

• Create a private constructor to prevent direct instantiation of the class.

• Create a private static instance of the class.

• Create a public static method to access the instance, and create the instance if it doesn't exist.

• Ensure thread safety by using synchronized keyword or double-checked locking.

Vector is synchronized and ArrayList is not. Vector is thread-safe and ArrayList is not.

• Vector is a legacy class and ArrayList is a part of the Java Collection Framework.

• Vector is synchronized which means only one thread can access it at a time, while ArrayList is not.

• Vector is thread-safe which means it can be used in a multi-threaded environment, while ArrayList is not.

• Vector is slower than ArrayList because of synch...read more

Create Linked List without using internal library and provide add, delete, find functionality.

• Create a Node class with data and next pointer

• Create a LinkedList class with head pointer and methods to add, delete, and find nodes

• Use a loop to traverse the list and perform operations

• Handle edge cases such as adding to an empty list or deleting the head node

The current system follows a microservices architecture.

• The system is divided into multiple independent services.

• Each service has its own database and communicates with other services through APIs.

• The architecture allows for scalability and flexibility.

• Examples of microservices used in the system include user authentication, payment processing, and inventory management.

Find the total no of islands in a 2D matrix.

• Use DFS or BFS to traverse the matrix.

• Mark visited cells to avoid repetition.

• Count the number of islands found.

Loop detection in a linked list.

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

• If there is a loop, the faster pointer will eventually catch up to the slower one.

• If there is no loop, the faster pointer will reach the end of the list.

My day was productive and fulfilling. As for myself, I am a driven and detail-oriented individual with a passion for problem-solving.

• I tackled several challenging tasks at work and made significant progress on each of them.

• I also took some time to exercise and clear my mind, which helped me stay focused throughout the day.

• As for myself, I have a background in engineering and enjoy using my analytical skills to find cre...read more

Optimizing code involves identifying and removing bottlenecks to improve performance.

• Identify the parts of the code that are taking the most time to execute

• Use efficient algorithms and data structures

• Minimize the number of function calls and loops

• Avoid unnecessary calculations or operations

• Use caching or memoization to avoid repeating calculations

• Profile the code to measure performance improvements

Optimized version of given code

• Use efficient data structures and algorithms

• Avoid unnecessary loops and conditions

• Minimize function calls and variable assignments

My day was productive and fulfilling. As for myself, I am a driven and detail-oriented individual with a passion for problem-solving.

• I tackled several challenging tasks at work and made significant progress on each of them.

• I also took some time to exercise and clear my mind, which helped me stay focused throughout the day.

• As for myself, I have a background in engineering and enjoy applying my analytical skills to a var...read more

Yes, I prefer coding in C and have read The C Programming Language book. I have also explored the concept of Inheritance in C.

• I find C to be a powerful and efficient language for system programming.

• Yes, I have read The C Programming Language book by Dennis Retchie and found it to be a great resource.

• Recently, I have been exploring the concept of Inheritance in C through various online resources and tutorials.

• While C do...read more

Inheritance allows a class to inherit properties and methods from another class.

• Inheritance promotes code reusability and saves time and effort in programming.

• It allows for the creation of a hierarchy of classes with shared characteristics.

• For example, a class Animal can be inherited by classes such as Dog, Cat, and Bird, which share common properties and methods.

• Inheritance can be implemented using the 'extends' keywo

Liskov substitution principle is a principle in object-oriented programming that states that objects of a superclass should be able to be replaced with objects of its subclasses without affecting the correctness of the program.

• Subtypes must be substitutable for their base types

• Derived classes must not change the behavior of the base class

• Violating the principle can lead to unexpected behavior and errors

• Example: A squar...read more

Explanation of OOPs concepts with programs

• Encapsulation: Wrapping data and functions into a single unit. Example: Class in Java

• Abstraction: Hiding implementation details and showing only necessary information. Example: Abstract class in C#

• Inheritance: Acquiring properties and behavior of a parent class. Example: Child class extending parent class in Python

• Polymorphism: Ability of an object to take many forms. Example:

Dynamic polymorphism is achieved through virtual functions and inheritance in object-oriented programming.

• Create a base class with virtual functions

• Create derived classes that override the virtual functions

• Use pointers or references of the base class to call the virtual functions

• The appropriate derived class function will be called based on the object being pointed to or referred to

Global variables can lead to unexpected changes and make debugging difficult.

• Global variables can be accessed and modified from any part of the code, making it difficult to track changes.

• They can cause naming conflicts if multiple variables with the same name are used in different parts of the code.

• Using global variables can make it harder to test and debug code, as it can be difficult to isolate the cause of errors.

• Th...read more

Using 'goto' can make code hard to read, maintain and debug.

• Goto statements can create spaghetti code that is difficult to follow.

• It can make it harder to understand the flow of the program.

• It can also make debugging more difficult.

• There are usually better alternatives to using goto, such as using loops or functions.

• Some programming languages, such as Java and Python, do not even have a goto statement.

• Using goto can al...read more

My favorite subject is history because it helps me understand the present and learn from the past.

• I enjoy learning about different cultures and how they have evolved over time

• I find it fascinating to study the causes and effects of major historical events

• One of my favorite books on history is 'Guns, Germs, and Steel' by Jared Diamond

Implicit objects are pre-defined objects in JSP that can be accessed without being explicitly declared.

• Implicit objects are created by the JSP container during the translation phase.

• They can be accessed using predefined names such as request, response, session, application, out, pageContext, config, and exception.

• For example, the request object can be used to retrieve parameters from a form or URL.

• The session object ca...read more

Apache is a popular web server and Tomcat is a widely used application server.

• Apache is an open-source web server that supports multiple operating systems and is known for its stability and security.

• Tomcat is a Java-based application server that is used to deploy Java web applications and supports servlets and JSPs.

• Other popular web servers include Nginx and Microsoft IIS.

• Other popular application servers include JBoss...read more

To deploy a web application on Apache Tomcat, the application needs to be packaged as a WAR file and then deployed to the Tomcat server.

• Create a WAR file of the web application

• Copy the WAR file to the Tomcat webapps directory

• Start the Tomcat server

• Access the web application using the URL http://localhost:8080/

• Collections in Java are classes that implement collections of objects, such as lists, sets, and