编写程序,定义一个接口 Compute,声明计算周长calgirth()和面积calarea ()的方法,然后定义一个长方形类RRect和圆类Circle,两个类都实现接口 Compute,最后编写测试类进行测试

好的，这是一个关于编写程序的问题，我可以回答。

首先，定义接口 Compute，声明计算周长 calgirth() 和面积 calarea() 的方法：

public interface Compute {
    public double calgirth();
    public double calarea();
}

然后，定义长方形类 RRect 和圆类 Circle，两个类都实现接口 Compute：

public class RRect implements Compute {
    private double length;
    private double width;

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

    public double calgirth() {
        return 2 * (length + width);
    }

    public double calarea() {
        return length * width;
    }
}

public class Circle implements Compute {
    private double radius;

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

    public double calgirth() {
        return 2 * Math.PI * radius;
    }

    public double calarea() {
        return Math.PI * radius * radius;
    }
}

最后，编写测试类进行测试：

public class Test {
    public static void main(String[] args) {
        RRect r = new RRect(3, 4);
        Circle c = new Circle(5);

        System.out.println("The girth of RRect is " + r.calgirth() + ", and the area is " + r.calarea() + ".");
        System.out.println("The girth of Circle is " + c.calgirth() + ", and the area is " + c.calarea() + ".");
    }
}

输出结果应该为：

The girth of RRect is 14.0, and the area is 12.0.
The girth of Circle is 31.41592653589793, and the area is 78.53981633974483.

希望这个回答能够帮到您！