What happens when Java executes Student s1 = new Student(10, "Kumar", 84.5)?

Java creates a new Student object on the heap by calling its constructor, then stores a reference to that object in s1.

Which Java access modifier permits access within the same package and by subclasses in other packages?

The protected modifier allows access from the same package and from subclasses, including subclasses in different packages.

How can custom Java objects be sorted in their natural order?

Implement the Comparable interface and define the compareTo() method to specify the class's natural ordering.

Free Course Image Object Oriented Programming in Java

Free online course Object Oriented Programming in Java

Duration of the online course: 9 hours and 14 minutes

New

Write cleaner Java with OOP skills—inheritance, interfaces, generics and collections. Learn online in a free course and earn a certificate-worthy foundation.

In this free course, learn about

Core OOP concepts in Java: classes, objects, constructors, and object creation with new
How fields/constructors initialize objects (e.g., Student s1 = new Student(...))
Packages and imports; using built-in methods and understanding Java's standard libraries
Static members: class-level fields/methods, initialization order, and static blocks
Singleton pattern: intent, implementation, and when to use it
OOP principles: inheritance, polymorphism, encapsulation, abstraction
Polymorphism details: reference type vs object type; method overriding and dynamic dispatch
Access control: modifiers, package-private behavior, and protected access across packages
Object class fundamentals: toString, equals, hashCode, cloning basics
Abstract classes vs interfaces; multiple inheritance via interfaces; annotations overview
Generics and type safety; building a custom ArrayList; lambda expressions basics
Exception handling patterns and best practices (try/catch/finally, throws, custom exceptions)
Natural ordering and sorting: implementing Comparable/Comparator for collections
Collections Framework essentials: List behaviors, Vector vs ArrayList, and enums usage

About the free online course

Build Java programs that are easier to maintain, extend, and scale by mastering object oriented programming from the ground up. This free online course guides you from the moment an object is created in memory to the design decisions that make real applications resilient over time. You will learn to think in terms of classes, objects, and responsibilities so your code reads clearly, avoids duplication, and stays flexible as requirements change.

You will practice core OOP principles—encapsulation, inheritance, polymorphism, and abstraction—and understand when each one improves design rather than complicates it. Along the way, you will work with packages, access control, and the Object class, helping you write code that behaves predictably across modules and teams. You will also gain confidence with static members, singleton-style patterns, and the built-in methods Java developers use daily.

As you progress, you will connect OOP to modern Java development by exploring abstract classes, interfaces, and annotations, including how Java supports multiple inheritance through interfaces. You will deepen your skills with generics to create type-safe components, and see how custom data structures can be designed with OOP thinking. The course also introduces practical features used in professional codebases, such as lambda expressions, exception handling, object cloning, and natural ordering for sorting objects.

Finally, you will become comfortable navigating the Collections Framework, understanding common list behaviors, legacy classes like Vector, and how enums fit into clean design. By the end, you will have a strong foundation to read and write idiomatic Java, contribute to backend projects, and approach interviews and assignments with a clear mental model of how OOP works in Java.

Course content

Video class: OOP 1 | Introduction 1h42m
Exercise: In Java OOP, what happens when you write Student s1 = new Student 10, Kumar, 84.5
Video class: OOP 2 | Packages, Static, Singleton Class, In-built Methods 1h19m
Exercise: Static members in Java
Video class: OOP 3 | Principles - Inheritance, Polymorphism, Encapsulation, Abstraction 2h12m
Exercise: Reference type vs object type in polymorphism

Video class: OOP 4 | Access Control, In-built Packages, Object Class 50m
Exercise: Which access modifier allows access in the same package and in subclasses of different packages in Java?
Video class: OOP 5 | Abstract Classes, Interfaces, Annotations 1h10m
Exercise: Java OOP Multiple Inheritance and Interfaces
Video class: OOP 6 | Generics, Custom ArrayList, Lambda Expressions, Exception Handling, Object Cloning 1h31m
Exercise: How do you enable natural ordering so objects of a class can be sorted in Java

Video class: OOP 7 | Collections Framework, Vector Class, Enums in Java 26m
Exercise: Which statement about Java's List in the Collections Framework is correct?

Free online courses on Object Oriented Programming

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Explore free online Object Oriented Programming courses and build practical skills in classes, objects, inheritance, polymorphism, encapsulation, and popular OOP languages. Learn at your own pace with beginner-friendly lessons, hands-on projects, and expert guidance. Enroll today and earn a certificate to showcase your programming skills.

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Explore free online Java courses with certificates and learn essential programming skills at your own pace. Master Java fundamentals, object-oriented programming, data structures, APIs, and application development through beginner-friendly and advanced lessons. Enroll today to build job-ready skills, strengthen your resume, and earn a certificate for free.