判断圆、三角形、长方形，并分别求出它们的周长和面积

import java.util.Scanner;
public class Circle2
{ 
 public static void main(String args[]){
  Scanner sc = new Scanner (System.in);
  System.out.println("请选择圆、长方形、三角形");
  int i = sc.nextInt();
  final double PI = 3.14;
  double c,s;
  switch (i)
  {
  case 1 :{
    System.out.println("请输入圆的半径：");
    double r = sc.nextDouble();
    c = PI * r * 2;
    s=  PI * r * r;
    System.out.println("圆的周长为" + c );
    System.out.println("圆的面积为" + s ) ;
    break;
   }
   case 2:{
    System.out.println("请输入长方形的长和宽：");
    double a = sc.nextDouble();
    double b = sc.nextDouble();
    c = (a + b ) * 2;
    s = a * b;
    System.out.println("长方形的周长为" + c );
    System.out.println("长方形的面积为" + s ) ;
    break;
   }
   case 3:{
    System.out.println("请分别输入三角形的三边和高：");/*注释：第一次输入的边为三角形的底，即x1为三角形的底*/
    double x1 = sc.nextDouble();
    double x2 = sc.nextDouble();
    double x3 = sc.nextDouble();
    double y = sc.nextDouble();
    c = x1 + x2 + x3;
    s = x1 * y / 2;
    System.out.println("三角形的周长为" + c );
    System.out.println("三角形的面积为" + s ) ;
    break;
   }
   default:{
    System.out.println("您输入的数值有误，请重新输入");
    break;
   }
  }
 }

}