object oriented programming

Object oriented programming languages include:

Java
JavaScript
Python
C++
Visual Basic .NET
Ruby
Scala
PHP

These are just the main ones, there's much more out there.

Abstraction (Partial Abstraction & Interfaces)
Encapsulation (Private Field & Getter & Setter)
Inheritance (Super and Sub Class)
Polymorphism (Static - Overloading & Dynanmic - Overriding)

class Person {
 void walk() {
  System.out.println(“Can Run….”);
 }
}
class Employee extends Person {
 void walk() {
  System.out.println(“Running Fast…”);
 }
 public static void main(String arg[]) {
  Person p = new Employee(); //upcasting
  p.walk();
 }
}

//	OOP is a programming paradigm found in many languages today.
//	Generally, an object is an instance of a Class.
//	Here's a Java example:
public class Car
{
	private double speed;
  	
  	public Car(double initialSpeed)	//	Constructor, most common way to initialize objects of a class.
    {
    	speed = initialSpeed;
    }
  
  	//	Accessor methods, aka getters
  	public double getSpeed()
    {
		return speed;
     	//	This is an example of encapsulation, where
      	//	methods are used to hide the implementation details
		//	and ensure the programmer can't modify things they shouldn't be able to.
    }
  
  	public void accelerate()
    {
		speed++;
    }
  
  	public void slowDown()
    {
    	speed--;
    }
}

  -- look up for `k' in list of tables `plist'
    local function search (k, plist)
      for i=1, table.getn(plist) do
        local v = plist[i][k]     -- try `i'-th superclass
        if v then return v end
      end
    end
    
    function createClass (...)
      local c = {}        -- new class
    
      -- class will search for each method in the list of its
      -- parents (`arg' is the list of parents)
      setmetatable(c, {__index = function (t, k)
        return search(k, arg)
      end})
    
      -- prepare `c' to be the metatable of its instances
      c.__index = c
    
      -- define a new constructor for this new class
      function c:new (o)
        o = o or {}
        setmetatable(o, c)
        return o
      end
    
      -- return new class
      return c
    end