java notes

Inheritance:A is a B relationship.

polymorphism:When you send a message to an object, the object will do the right
thing, even when upcasting is involved.

Sample:

void doStuff(Shape s) {
s.erase();
// ...
s.draw();
}

Circle c = new Circle();
Triangle t = new Triangle();
Line l = new Line();
doStuff(c);
doStuff(l);doStuff(t);