Abstract Classes

An abstract class may contain abstract methods, that is, methods with no implementation. An abstract class leaves some of the implementation to its subclasses.

abstract class GraphicObject {
    int x, y;
    . . .
    void moveTo(int newX, int newY) {
        . . .
    }
    abstract void draw();
}

class Circle extends GraphicObject {
    void draw() {
        . . .
    }
}

class Rectangle extends GraphicObject {
    void draw() {
        . . .
    }
}

An abstract class cannot be instantiated.