Lenovo Web Developer Interview Questions and Answers

Oops concepts in Java

• Encapsulation - hiding implementation details

• Inheritance - reusing code and creating parent-child relationships

• Polymorphism - multiple forms of a method or object

• Abstraction - creating abstract classes and interfaces

• Example: Encapsulation - using private variables and public methods

• Example: Inheritance - creating a subclass that inherits from a superclass

• Example: Polymorphism - using method overloa...read more

Altering columns in databases involves modifying the structure of a table by adding, deleting or modifying columns.

• Use ALTER TABLE statement to modify columns

• Add new columns using ADD COLUMN

• Delete columns using DROP COLUMN

• Modify columns using MODIFY COLUMN

• Changing column data type may result in data loss

Reversing a number in Java

• Convert the number to a string

• Use StringBuilder to reverse the string

• Convert the reversed string back to a number

To extract words from a line in Java, split the line using whitespace as delimiter.

• Use the split() method of String class

• Pass the whitespace regex as argument to split() method

• Iterate over the resulting array to get individual words

C# concepts including abstraction, interface, abstract method, abstract class, polymorphism, encapsulation, inheritance, and serialization.

• Abstraction: hiding implementation details

• Interface: defining a contract for behavior

• Abstract method: method without implementation

• Abstract class: class with one or more abstract methods

• Polymorphism: ability of objects to take on multiple forms

• Encapsulation: bundling data and behavi...read more