输出某个年龄的人的比例
package ch06; import java.math.BigDecimal; import java.util.Scanner; /** * Created by liwenj on 2017/7/18. */ public class test5 { //除法 public static double div(double v1, double v2, int scale) { if (scale < 0) { throw new IllegalArgumentException( "The scale must be a positive integer or zero"); } BigDecimal b1 = new BigDecimal(Double.toString(v1)); BigDecimal b2 = new BigDecimal(Double.toString(v2)); return b1.divide(b2, scale, BigDecimal.ROUND_HALF_UP).doubleValue(); } //精确的乘 public static double mul(double v1, double v2) { BigDecimal b1 = new BigDecimal(Double.toString(v1)); BigDecimal b2 = new BigDecimal(Double.toString(v2)); return b1.multiply(b2).doubleValue(); } public static void main(String[] args) { Scanner input = new Scanner(System.in); int big = 0; for (int i = 1; i < 4; i++) { System.out.print("请输入第" + i + "个顾客的年龄"); int age = input.nextInt(); if (age > 30) { big++; } } double r=div(big,3,3);//第二个参数是输入的个数,是第三个参数是保留的小数个数; System.out.println(r); double x=mul(r,100);//第二个参数是乘数100; System.out.println("大于30岁的人" + x + "%"); } }