Question

Can somebody explain to me the main differences between the principles of encapsulation and abstraction in objected-oriented programming (if possible with examples).

Answer 1

Sample:

// NO ABSTRACTION, NO ENCAPSULATION
const int catLegs = 4;
const int spiderLegs = 8;

Leg[] catLegs;
Leg[] spiderLegs;

void MakeCatRun(Distance b) { for (int i=0; i<catLegs; ++i) catLegs[i] += b; }
void MakeSpiderRun(Distance b) { for (int i=0; i<spiderLegs; ++i) spiderLegs[i] += b; }

Encapsulation:

// ENCAPSULATION
class Cat
{
    Leg[] legs;
    int nLegs;

    public void Run(Distance b) { for (int i=0; i < nLegs; ++i) leg[i] += b; }
}

class Spider
{
    Leg[] legs;
    int nLegs;

    public void Run(Distance b) { for (int i=0; i < nLegs; ++i) leg[i] += b; }
}

Abstraction:

 // ABSTRACTION
    class LivingBeing
    {
        Leg[] legs;
        int nLegs;

        public void Run(Distance b) { for (int i=0; i < nLegs; ++i) leg[i] += b; }
    }

    class Cat: LivingBeing       {        }

    class Spider: LivingBeing   {    }