Shape接口： /** * @version V 1.0 * @Descriptyion : * @Author:hsfxuebao * @Date 2018/3/14 20:09 * @Modified By : */ public interface Shape { double area(double radius); } Circle类： public class Circle implements Shape { @Override public double area(double radius) { return Math.PI * radius * radius; } } Square类： public class Square implements Shape { @Override public double area(double radius) { return radius * radius; } } 测试方法： public class TestShape { public static void main(String[] args) { Shape circle = new Circle(); Shape square = new Square(); int number = 2; int radius = 3; //计算正方形的面积 System.out.println(square.area(number)); //计算圆形的面积 System.out.println(circle.area(radius)); } } 运行结果： 4.0 28.274333882308138