OOP (Learn & Practice)
Asked in almost every fresher interview: classes, the four pillars, and how objects behave.
About OOP (Learn & Practice)
Object-oriented programming (OOP) organises code around objects: bundles of data and the behaviour that works on it. A class is the blueprint; an object is one thing built from it.
Its four pillars are encapsulation, abstraction, inheritance and polymorphism. Java, C++, Python and C# all use these ideas.
Why it matters for placements
Almost every fresher interview has OOP questions, from "what is polymorphism?" to predicting the output of overloaded and overridden methods. It is also the base for Low Level Design.
What you'll learn
4 topics · 15 lessons, each with practice
- Explain the four pillars with your own examples
- Write classes with constructors, access modifiers and static members
- Use inheritance, abstract classes and interfaces correctly
- Predict the output of overloading and overriding questions
- Choose composition over inheritance where it fits
Foundation Foundation
Take Foundation testRequired. Enough to clear online assessments and service-company interviews.
Classes & Objects
Not startedClasses and objects are how Java groups related data and the code that works on it. Almost every fresher interview starts here, with questions on constructors, this and static, and many output questions depend on knowing how objects and references behave.
Four Pillars
Not startedEncapsulation, inheritance, polymorphism and abstraction are the ideas that make object-oriented code easier to change and reuse. "Explain the four pillars with an example" is one of the most common fresher interview questions, so you need both the definition and a real use for each.
Interview Ready Interview Ready
Take Interview Ready testRecommended. Enough for technical rounds at good product companies.
OOP in Depth
Not startedAfter the basics, interviewers test the details: which tool to pick, how Java decides which method to call, and who can see what. These topics are where most "predict the output" and "will this compile?" questions come from.
Object Behaviour
Not startedObjects behave in surprising ways when you compare, share or copy them. These topics explain why == and equals() differ, why some objects should never change, and why a copy can still change the original.