根据下面的继承关系，用 java 代码实现 (1) Circle 类(圆形） 属性：半径；方法：1求周长、求面和 (2)Rect 类（矩形 求周- (3) Square 类(正方形)，属性：边长；方法：求周长、求面积

在 Java 中，我们可以按照继承结构创建这三个类，并实现相应的属性和方法。首先，我们创建一个 `Shape` 接口作为基础类型：

// Shape接口
public interface Shape {
    double getArea();
    double getPerimeter();
}

然后分别实现 `Circle`, `Rect`, 和 `Square` 类，它们都继承自 `Shape` 并提供各自特有的属性和方法：

// Circle类
public class Circle implements Shape {
    private double radius;

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

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

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

// Rect类
public class Rect implements Shape {
    private double width;
    private double height;

    public Rect(double width, double height) {
        this.width = width;
        this.height = height;
    }

    @Override
    public double getArea() {
        return width * height;
    }

    @Override
    public double getPerimeter() {
        return 2 * (width + height);
    }
}

// Square类
public class Square extends Rect implements Shape {
    public Square(double sideLength) {
        super(sideLength, sideLength); // 使用边长作为宽度和高度
    }
}

现在你可以使用这些类创建实例并调用它们的方法：

public static void main(String[] args) {
    Circle circle = new Circle(5);
    System.out.println("Circle area: " + circle.getArea());
    System.out.println("Circle perimeter: " + circle.getPerimeter());

    Rect rect = new Rect(4, 6);
    System.out.println("Rect area: " + rect.getArea());
    System.out.println("Rect perimeter: " + rect.getPerimeter());

    Square square = new Square(3);
    System.out.println("Square area: " + square.getArea());
    System.out.println("Square perimeter: " + square.getPerimeter());
    
    // 测试 Square 类的多态
    Shape shape = square; // 这里 shape 可以同时处理 Square 或者其他实现了 Shape 的类
    System.out.println("Square area as a Shape: " + shape.getArea());
    System.out.println("Square perimeter as a Shape: " + shape.getPerimeter());
}