@startuml
' 形状类图

' 抽象类 Shape
abstract class Shape {
    + getArea(): double
}

' Circle 类
class Circle {
    - radius: double
    + Circle(radius: double)
    + getArea(): double
}

' Rectangle 类
class Rectangle {
    - width: double
    - height: double
    + Rectangle(width: double, height: double)
    + getArea(): double
}

' Triangle 类
class Triangle {
    - base: double
    - height: double
    + Triangle(base: double, height: double)
    + getArea(): double
}

' ShapeUtil 工具类
class ShapeUtil {
    + printArea(shape: Shape): void
    + main(args: String[]): void
}

' 继承关系
Shape <|-- Circle
Shape <|-- Rectangle
Shape <|-- Triangle

' 使用关系
ShapeUtil --> Shape

@enduml