类与对象（）

1.   编写3个基本类： Triangle, Ladder和Circle，分别用来刻画“三角形”、“梯形”和“圆形”类； 1个主类： Compute，负责计算每个形状的面积或周长。

具体要求：

Ÿ  Triangle 定义3个变量：边长；和1个求周长的方法。

Ÿ  Ladder  定义3个变量：上底，下底和高；定义1个求面积的方法。

Ÿ  Circle   定义1个变量：半径；定义2个方法：求面积、求周长。

Ÿ  3个基本类都要定义相应的构造方法，对变量进行初始化。

package shiyan4;public class Circle {private double r;//半径public Circle() {}public Circle(double r) {this.r = r;}public double getR() {return r;}public void setR(double r) {this.r = r;}/** * 计算周长 * @return */public double Length(){return Math.PI*r*2;}/** * 计算面积 * @return */public double Area(){return Math.PI*r*r;}}

package shiyan4;public class Computer {/** * @param args */public static void main(String[] args) {// TODO Auto-generated method stubCircle c=new Circle(3);System.out.println("圆半径为3，周长："+c.Length()+"面积："+c.Area());System.out.println("梯形上底为2，下底为3，高是4，面积："+new Ladder(2,3,4).Area());System.out.println("三角形三边长分别是：2，3，4，周长："+new Triangle(2,3,4).Length());System.out.printf("圆半径为3，周长：%f面积：%f \n",c.Length(),c.Area());System.out.printf("梯形上底为2，下底为3，高是4，面积：%f \n",new Ladder(2,3,4).Area());System.out.printf("三角形三边长分别是：2，3，4，周长：%f \n",new Triangle(2,3,4).Length());}}

package shiyan4;public class Ladder {private double up;private double down;private double hight;public Ladder() {}public Ladder(double up, double down, double hight) {super();this.up = up;this.down = down;this.hight = hight;}public double getUp() {return up;}public void setUp(double up) {this.up = up;}public double getDown() {return down;}public void setDown(double down) {this.down = down;}public double getHight() {return hight;}public void setHight(double hight) {this.hight = hight;}/** * 计算面积 * @return */public double Area(){return (up+down)*hight/2;}}

package shiyan4;public class Triangle {private double a;private double b;private double c;public Triangle() {}public Triangle(double a, double b, double c) {this.a = a;this.b = b;this.c = c;}public double getA() {return a;}public void setA(double a) {this.a = a;}public double getB() {return b;}public void setB(double b) {this.b = b;}public double getC() {return c;}public void setC(double c) {this.c = c;}/** * 计算周长 * @return */public double Length(){return a+b+c;}/** * 计算面积 * @return */public double Area(){double p =(a+b+c)/2;return Math.sqrt(p*(p-a)*(p-b)*(p-c));}}