OOP Across Languages

Same ideas, different mechanisms

Languages implement OOP differently. Java and C#: class-based, single class inheritance, multiple interfaces, garbage collection, every method virtual by default in Java (C# requires virtual). C++: classes with multiple inheritance, virtual functions for dynamic dispatch, deterministic destructors and RAII, value and reference semantics both available. Python: everything is an object, multiple inheritance with a method resolution order, duck typing, no enforced privacy, special methods for operators, and dataclasses for value types. JavaScript: prototype-based inheritance; the class keyword (ES2015) is syntax over prototypes, with private fields using #. Go: no classes or inheritance; structs with methods, embedding for composition and implicit, structural interfaces. Rust: structs and enums with methods, traits for shared behaviour (with static or dynamic dispatch through dyn Trait), no implementation inheritance. Kotlin and Swift favour final-by-default classes and value types. Understanding the principles lets you apply them in any of these languages.

Polymorphism in Python and Go

Both achieve "one interface, many implementations" without Java-style declarations.

# Python: duck typing plus an abstract base class for documentation and checks
from abc import ABC, abstractmethod
import math

class Shape(ABC):
    @abstractmethod
    def area(self) -> float: ...

class Circle(Shape):
    def __init__(self, r: float):
        self.r = r
    def area(self) -> float:
        return math.pi * self.r ** 2

class Square(Shape):
    def __init__(self, side: float):
        self.side = side
    def area(self) -> float:
        return self.side ** 2

total = sum(s.area() for s in [Circle(1), Square(2)])

# Go: structural interfaces, no 'implements' keyword
# type Shape interface { Area() float64 }
# type Square struct { Side float64 }
# func (s Square) Area() float64 { return s.Side * s.Side }   // Square satisfies Shape implicitly

Different scripts, same language of ideas

Hindi can be written in Devanagari or transliterated in Latin letters; the meaning stays the same. OOP principles are the meaning, and each programming language is a different script for expressing them.

Quick check: Which language implements interfaces structurally, so a type satisfies an interface just by having its methods?

• Java
• Go
• C#
• C++