笔记14 多态

package test0909;
/*
 *   1、什么是多态？
 *    1) 生活角度：  龙生九子，各有不同； 
 *    2) 专业角度： 一个类中的属性和方法在子类中通过各自不同的实现，可以具有不同的数据类型或者不同的行为 
 * 
 *   2、多态在java中的形式:
 *    父类的对象变量引用子类的对象。
 *    例如:  Person p1 = new Student()
 */
public class ShapeTest{
	public static void main(String[] args) {
		Shape [] a = new Shape [5];
		
		for (int i = 0; i < a.length ; i++){
			a[i] = type() ;
		}
		//求各个图形的面积，和总面积
		double total = 0;
		for(int i = 0; i < a.length; i++){
			System.out.println(a[i].toString());
			total += a[i].area();
		}
		System.out.println("总面积为："+ total);
	}
	public static Shape type(){
		int n = (int)(3 * Math.random());
		if(n == 0){
			return new Circle("圆形", (int)(10 * Math.random()) );
		}else if(n == 1){
			return new Rectangle("矩形", (int)(10 * Math.random()), (int)(10 * Math.random()) );
		}else{
			return new Triangular("" , (int)(10 * Math.random()), (int)(10 * Math.random()) );
		}
	}
}

class Shape {
	private String type;
	
	public Shape() {
	
	}
	public Shape(String type){
		this.type = type;
	}
	
	public void setType(String type) {
		this.type = type;
	}
	public String getType() {
		return type;
	}
	
	//功能方法，求图形的面积；
	 public double area(){
		 return 0;
	 }
	 public String toString(){
		 return "平面图形的种类：" + type ;
	 }
}
class Circle extends Shape{
	private int r;
	
	public Circle() {	
	}
	public Circle(String type, int r){
		super( type );
		this.r = r;
	}
	
	public void setR(int r) {
		this.r = r;
	}
	public int getR() {
		return r;
	}
	
	//重写area方法，求面积；
	public double area(){
		return Math.PI * r * r ;
	}
	@Override
	public String toString() {
		return super.toString() + " 圆的半径为：" + r + " 面积为:" + area() ;
	}
}

class Rectangle extends Shape {
	private int w;
	private int h;
	public Rectangle() {
	}
	public Rectangle(String type, int w, int h){
		super( type );
		this.w = w;
		this.h = h;		
	}
	public int getW() {
		return w;
	}
	public void setW(int w) {
		this.w = w;
	}
	public int getH() {
		return h;
	}
	public void setH(int h) {
		this.h = h;
	}
	// 改写功能方法，计算矩形的面积；
	public double area() {
		return w * h ;
	}
	public String toString(){
		return super.toString() + " 矩形的宽为：" + w + " 矩形的高：" + h + " 矩形的面积为：" + area() ;
	}
}

class Triangular extends Shape{
	private int a;
	private int h;
	public Triangular() {
	}
	public Triangular(String type, int a, int h){
		super( type );
		this.a = a;
		this.h = h;
	}
	public int getA() {
		return a;
	}
	public void setA(int a) {
		this.a = a;
	}
	public int getH() {
		return h;
	}
	public void setH(int h) {
		this.h = h;
	}
	//编写功能方法，求矩形的面积；
	@Override
	public double area() {
		return a * h / 2.0 ;
	}
	public String toString(){
		return super.toString() + " 三角形的底边长：" + a + " 高为：" + h + " 面积是：" + area() ;
	}
}