Java - 程序在不应该接受负数时接受

Question

我必须编写一个程序，使用嵌套循环来收集数据并计算几年内的平均降雨量。首先，程序应该询问年数。 （外循环将每年迭代一次。）内循环将迭代 12 次，每月一次。内部循环的每次迭代都会询问用户该月的降雨量。在所有迭代之后，程序应显示月数、总降雨量以及整个期间每月的平均降雨量。

输入验证：不接受小于 1 的数字作为年数。每月降雨量不接受负数。

我已经完成了程序，但是有一个小问题：当它要求输入英寸时，如果我输入 1 表示年份，它会要求我输入英寸 12 次。如果我先输入一个负数，它会告诉我该数字无效，然后再次循环并要求我输入一个等于或大于零的数字。现在，如果我输入一系列 >=0 的数字，然后输入一个负数，它并没有告诉我我不能输入一个负数。它根本不应该接受负数，但是当前 2 个或更多数字 >= 零时它会接受。

import java.util.Scanner;

public class Averagerainfallteller {
   /**
    * This program tells asks the user to enter an amount of years and then asks
    * the user to given the amount of inches that fell for every month during
    * those years and then give the average rain fall, total inches of rain and
    * total months.
    */
   public static void main(String[] args) {

      double totalInches = 0; 
      double totalMonths = 0; 
      double avgInches = 0; 
      double inches = 0; 
      Scanner kb = new Scanner(System.in);
      System.out.println(" PLease enter the number of years");
      int numYears = kb.nextInt();
      while (!(numYears >= 1)) {
         System.out.println(" PLease enter the number that is more than or equal to one.");
         numYears = kb.nextInt();
      }

      for (int years = 1; years <= numYears; years++) {

         for (int months = 1; months <= 12; months++) {
            System.out.println("How many inches fell for Year: " + years
                  + ", during Month: " + months + "? ");
            inches += kb.nextDouble();
            while (!(inches >= 0)) {
               System.out.println("PLease enter the number that is more than or equal to zero.");
               System.out.println("How many inches fell for Year: " + years
                     + ", during Month: " + months + "? ");
               inches += kb.nextDouble();
            }
         }
      }

      totalMonths = 12 * numYears;
      avgInches = totalInches / totalMonths;
      System.out.println(".....HERE ARE THE RESULTS.....");
      System.out.println("");
      try {
         Thread.currentThread().sleep(1000);
      } catch (Exception e) {
      }
      System.out.println("    Total inches is " + totalInches);
      System.out.println("");
      try {
         Thread.currentThread().sleep(1000);
      } catch (Exception e) {
      }
      System.out.println("    Average Inches is " + avgInches);
      System.out.println("");
      try {
         Thread.currentThread().sleep(1000);
      } catch (Exception e) {
      }
      System.out.println("    Total months is " + totalMonths);
   }
}

Answer 1

不要使用inches +=kb.nextDouble();，而是使用input = kb.nextDouble(); if input > 0 then inches += input; otherwise loop。这应该可以帮助您在算术逻辑之前过滤掉负数。

Answer 2

问题是这样的：

inches += kb.nextDouble();

试试这个：

System.out.println("How many inches fell for Year: "+years+", during Month: "+months+ "? ");
inches = kb.nextDouble();    //HERE

while(!(inches>=0))
{


    System.out.println("PLease enter the number that is more than or equal to zero.");
    System.out.println("How many inches fell for Year: "+years+", during Month: "+months+ "? ");
    inches =kb.nextDouble();    //HERE

}

totalInches += inches;    //HERE

基本上，您继续将用户输入的数字连续添加到同一变量inches。此外，您似乎使用 totalInches 而不对其进行初始化，因此它始终为零。

Answer 3

确保为inches（非负数）输入了一个新值，然后将其添加到totalInches。

for (int months = 1; months <= 12; months++) {

    do {
        System.out.println("How many inches fell for Year: " + years + ", during Month: " + months + "? ");
        inches = kb.nextDouble();
    }while(inches < 0);

    totalInches += inches;
}