Question

JAVA用接口设计并实现圆,三角形,矩形的面积与周长计算

要求：①定义一个接口，其中包含一个计算面积的抽象方法和一个计算周长的抽象方法；②输入数据为圆的半径、三角形的三条边长、矩形的长和宽，对于用户的输入要有友好提示；③程序能够排除输入过程中的非法数据（如：输入的长度数据为负数或字符；输入的三角形三条边数据不能组成三角形；④计算圆、三角形、矩形的面积和周长，并输出原始数据和结算结果。

Answer 1

package javaapplication3;
import java.util.Scanner;
interface Shape{
public abstract double getArea();
public abstract double getCircumference();
}

class Circle implements Shape {
private double r=0;
public Circle(double r) {
this.r=r;}
public double getR(){
return this.r; }
public double getArea() {
return (3.14*this.r*this.r);}
public double getCircumference(){
return 2*3.14*this.r;
}
}

class Triangle implements Shape {
private double a=0;
private double b=0;
private double c=0;
public Triangle(double a, double b, double c) {
this.a=a;
this.b=b;
this.c=c;}
public double getA() {
return this.a;}
public double getB() {
return this.b;}
public double getC() {
return this.c;}
public double getArea() {
// 根据海伦公式求三角形的面积
double p=(a+b+c)/2;
return Math.pow(p*(p-a)*(p-b)*(p-c),0.5);}
public double getCircumference(){
return this.a+this.b+this.c;
}
}

class Rentangle implements Shape{
public double height=0;
public double width=0;
public Rentangle(double height, double width){
this.height = height;
this.width = width;}
public double getHeight(){
return this.height; }
public double getWidth(){
return this.width;}
public double getArea(){
return this.height*this.width;
}
public double getCircumference(){
return 2*(this.height+this.width);
}
}

public class testshape {
public static void main(String[] args){
Scanner input = new Scanner(System.in);
double r=0;
double a=0;
double b=0;
double c=0;
double height=0;
double width=0;
do{
System.out.println("请输入圆的半径r：");
r= input.nextDouble();
if (r<=0) {
System.out.print("输入错误!!!");
}
}while (r<=0);

do {
System.out.println("请输入三角形的三条边a、b、c：");
a= input.nextDouble();
b= input.nextDouble();
c= input.nextDouble();
if (a<0||b<0||c<0||a+b<=c||a-b>=c) {
System.out.print("输入错误!!!");
}
} while ((a<0||b<0||c<0||a+b<=c||a-b>=c));

do {
System.out.println("请输入矩形的长和宽height、width：");
height= input.nextDouble();
width= input.nextDouble();
if (height<=0||width<=0) {
System.out.print("输入错误!!!");
}
} while (height<=0||width<=0);

Circle C=new Circle(r);
Triangle T=new Triangle(a,b,c);
Rentangle R=new Rentangle(height,width);

System.out.println("******圆*******");
System.out.println("半径: " + C.getR());
System.out.println("面积 : " + C.getArea());
System.out.println("周长 : " + C.getCircumference());

System.out.println("*******三角形*******");
System.out.println("三边为: " + T.getA()+","+T.getB()+","+T.getC());
System.out.println("面积 : " + T.getArea());
System.out.println("周长 : " + T.getCircumference());

System.out.println("*******矩形*******");
System.out.println("长: " + R.getHeight());
System.out.println("宽: " + R.getWidth());
System.out.println("面积 : " + R.getArea());
System.out.println("周长 : " + R.getCircumference());
}
}