程序功能：
使用继承和多态的面向编程思想，动态的判断几何形状，打印平面图形面积及立体几何图形的面积和体积。
这个习题让我从无到有创建了共10个类才完成，虽然简单，但是作为继承和多态的入门练习还是不错的！
测试结果：
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逐个处理：
circle's area:201.06 square's area:64.00 triangle's area:24.00 sphere's area:804.25 sphere's volume:2144.66 cube's area:384.00 cube's volume:512.00 tetrahedron's area:110.85 tetrahedron's volume:60.34
多态处理：
图形 0是一个圆 面积：201.06
图形 1是一个正方形 面积：64.00
图形 2是一个三角形 面积：24.00
图形 3是一个球 面积：804.25 体积：2144.66
图形 4是一个立方体 面积：384.00 体积：512.00
图形 5是一个圆 面积：110.85 体积：60.34
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代码：
1. 测试类
//Java How to Program, Exercise 10.13: Project: Shape Hierarchy
//by pandenghuang@163.com
/**
* 10.13 (Project: Shape Hierarchy) Implement the Shape hierarchy shown in Fig.
* 9.3. Each Two-DimensionalShape should contain method getArea to calculate the
* area of the two-dimensional shape. Each ThreeDimensionalShape should have
* methods getArea and getVolume to calculate the surface area and volume,
* respectively, of the three-dimensional shape. Create a program that uses an
* array of Shape references to objects of each concrete class in the hierarchy.
* The program should print a text description of the object to which each array
* element refers. Also, in the loop that processes all the shapes in the array,
* determine whether each shape is a TwoDimensionalShape or a
* ThreeDimensionalShape. If it’s a TwoDimensionalShape, display its area. If
* it’s a ThreeDimensionalShape, display its area and volume.
*
* @author Pandenghuang@163.com
* @Date Jan 7, 2019, 9:13:12 AM
*
*/
public class ShapeHierarchyTest {
public static void main(String[] args) {
Circle circle = new Circle(8);
Square square = new Square(8);
Triangle triangle = new Triangle (6,8,10);
Sphere sphere = new Sphere(8);
Cube cube = new Cube(8);
Tetrahedron tetrahedron = new Tetrahedron(8);
System.out.printf("逐个处理：%n%n");
System.out.printf("circle's area:%.2f%n", circle.getArea());
System.out.printf("square's area:%.2f%n", square.getArea());
System.out.printf("triangle's area:%.2f%n", triangle.getArea());
System.out.printf("sphere's area:%.2f%n", sphere.getArea());
System.out.printf("sphere's volume:%.2f%n", sphere.getVolume());
System.out.printf("cube's area:%.2f%n", cube.getArea());
System.out.printf("cube's volume:%.2f%n", cube.getVolume());
System.out.printf("tetrahedron's area:%.2f%n", tetrahedron.getArea());
System.out.printf("tetrahedron's volume:%.2f%n", tetrahedron.getVolume());
Shape[] shapes = new Shape[6];
shapes[0] = circle;
shapes[1] = square;
shapes[2] = triangle;
shapes[3] = sphere;
shapes[4] = cube;
shapes[5] = tetrahedron;
System.out.printf("%n%n多态处理：%n%n");
// get type name of each object in employees array
for (int j = 0; j < shapes.length; j++) {
String[] classInfo =shapes[j].getClass().getName().split("\\.");
String className = classInfo[classInfo.length-1];
String classNameCN = "圆";
switch (className) {
case "Circle":
classNameCN = "圆";
break;
case "Square":
classNameCN = "正方形";
break;
case "Triangle":
classNameCN = "三角形";
break;
case "Sphere":
classNameCN = "球";
break;
case "Cube":
classNameCN = "立方体";
break;
case "Terahedron":
classNameCN = "正四面体";
break;
}
System.out.printf("图形 %d是一个%s%n", j, classNameCN); //打印对象的类型（类名）
if (shapes[j] instanceof TwoDimensionalShape)
System.out.printf("面积：%.2f%n%n", shapes[j].getArea()); //如果是二维图形，打印面积
else if (shapes[j] instanceof ThreeDimensionalShape) {
ThreeDimensionalShape threeDimensionalShape = (ThreeDimensionalShape)shapes[j]; //如果是三维图形，打印面积和体积
System.out.printf("面积：%.2f%n", threeDimensionalShape.getArea());
System.out.printf("体积：%.2f%n%n", threeDimensionalShape.getVolume());
}
}
}
}
2. 实体类
1）Shape类（基类，图形）
/**
*
* @author Pandenghuang@163.com
* @Date Jan 7, 2019, 1:44:02 AM
*
*/
public abstract class Shape {
public abstract double getArea();
}
2）TwoDimensionalShape类 （平面图形）
public abstract class TwoDimensionalShape extends Shape {
}
3）ThreeDimensionalShape类 （立体图形）
public abstract class ThreeDimensionalShape extends Shape{
public abstract double getVolume();
}
4）Circle类 （圆）
public class Circle extends TwoDimensionalShape {
private double radius;
Circle(double radius){
this.radius = radius;
}
@Override
public double getArea() {
return Math.PI*Math.pow(radius,2);
}
}
5）Square类 （正方形）
public class Square extends TwoDimensionalShape{
private double sideLength;
Square(double sideLength){
this.sideLength = sideLength;
}
@Override
public double getArea() {
return Math.pow(sideLength,2);
}
}
6）Triangle类 （三角形）
public class Triangle extends TwoDimensionalShape {
private double a;
private double b;
private double c;
public Triangle (double a, double b, double c) {
this.a = a;
this.b = b;
this.c = c;
}
@Override
public double getArea() {
double p = (a + b + c)/2.0;
return Math.sqrt(p*(p-a)*(p-b)*(p-c));
}
}
7) Sphere类 （球）
public class Sphere extends ThreeDimensionalShape {
private double radius;
Sphere(double radius){
this.radius = radius;
}
@Override
public double getArea() {
return 4*Math.PI*Math.pow(radius,2);
}
@Override
public double getVolume() {
return 4.0/3.0*Math.PI*Math.pow(radius,3);
}
}
8）Cube类 （立方体）
public class Cube extends ThreeDimensionalShape {
private double length;
Cube(double length){
this.length = length;
}
@Override
public double getArea() {
return 6*Math.pow(length,2);
}
@Override
public double getVolume() {
return Math.pow(length,3);
}
}
9）Tetrahedron类（正四面体）
public class Tetrahedron extends ThreeDimensionalShape {
private double length;
Tetrahedron(double length){
this.length = length;
}
@Override
public double getArea() {
return Math.sqrt(3)*Math.pow(length,2);
}
@Override
public double getVolume() {
return Math.sqrt(2)/12*Math.pow(length,3);
}
}
本文地址：https://blog.csdn.net/hpdlzu80100/article/details/85985958
