Java Practice Arena
Object-Oriented Programming
Master every OOP concept with visual diagrams, clear explanations, and 120+ unique questions covering Classes, Encapsulation, Inheritance, Polymorphism, SOLID, Design Patterns and more.
Concepts:20
Questions:120
Score:0/0
OOP Concepts – Visual Guide
Click any card to expand diagrams, key points & Java examples
A class is a blueprint that defines the structure (fields) and behavior (methods) of objects. An object is a concrete instance of a class created at runtime with its own state.
Visual Sketch
Class
Blueprint
obj1
obj2
obj3
Key Points
- Class = template; Object = instance
- new ClassName() allocates memory on the heap
- Each object has its own copy of instance variables
- Methods are shared (stored once in method area)
Java Example
class Dog {
String name;
void bark() { System.out.println(name + " says woof"); }
}
Dog d1 = new Dog(); // object 1
d1.name = "Rex";
Dog d2 = new Dog(); // object 2
d2.name = "Max";