classDiagram
    class Shape {
        <<abstract>>
        +getArea() double*
    }
    class Circle {
        -radius : double
        +Circle(double)
        +getArea() double
    }
    class Rectangle {
        -length : double
        -width : double
        +Rectangle(double, double)
        +getArea() double
    }
    class Triangle {
        -base : double
        -height : double
        +Triangle(double, double)
        +getArea() double
    }
    class ShapeUtil {
        +printArea(Shape) void
    }
    Shape <|-- Circle
    Shape <|-- Rectangle
    Shape <|-- Triangle
    ShapeUtil --> Shape : uses