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