So lets say I have this interface:
public interface IBox
{
public void setSize(int size);
public int getSize();
public int getArea();
//...and so
The purpose of interfaces is polymorphism, a.k.a. type substitution. For example, given the following method:
public void scale(IBox b, int i) {
b.setSize(b.getSize() * i);
}
When calling the scale
method, you can provide any value that is of a type that implements the IBox
interface. In other words, if Rectangle
and Square
both implement IBox
, you can provide either a Rectangle
or a Square
wherever an IBox
is expected.