编写一个 Shape 接口，接口中有三个抽象方法 area ()、 perimeter ()、 get - ClassName ()，分别用于计算图形的面积、周长以及获取类的名称；设计类 Circle （圆形）、 Square （正方形）、 Rectangle （矩形），实现接口 Shape 中的所有方法。创建一个包含 main 方法的类测试相关的类和接口。

好的，以下是我给出的代码：

public interface Shape {
    double area();
    double perimeter();
    String getClassName();
}

public class Circle implements Shape {
    private double radius;

    public Circle(double radius) {
        this.radius = radius;
    }

    @Override
    public double area() {
        return Math.PI * radius * radius;
    }

    @Override
    public double perimeter() {
        return 2 * Math.PI * radius;
    }

    @Override
    public String getClassName() {
        return "Circle";
    }
}

public class Square implements Shape {
    private double side;

    public Square(double side) {
        this.side = side;
    }

    @Override
    public double area() {
        return side * side;
    }

    @Override
    public double perimeter() {
        return 4 * side;
    }

    @Override
    public String getClassName() {
        return "Square";
    }
}

public class Rectangle implements Shape {
    private double length;
    private double width;

    public Rectangle(double length, double width) {
        this.length = length;
        this.width = width;
    }

    @Override
    public double area() {
        return length * width;
    }

    @Override
    public double perimeter() {
        return 2 * (length + width);
    }

    @Override
    public String getClassName() {
        return "Rectangle";
    }
}

public class ShapeTest {
    public static void main(String[] args) {
        Shape circle = new Circle(5);
        Shape square = new Square(4);
        Shape rectangle = new Rectangle(3, 5);

        System.out.println(circle.getClassName() + " area: " + circle.area());
        System.out.println(circle.getClassName() + " perimeter: " + circle.perimeter());

        System.out.println(square.getClassName() + " area: " + square.area());
        System.out.println(square.getClassName() + " perimeter: " + square.perimeter());

        System.out.println(rectangle.getClassName() + " area: " + rectangle.area());
        System.out.println(rectangle.getClassName() + " perimeter: " + rectangle.perimeter());
    }
}

希望这个代码能够满足你的需求！