输出两个整数之间偶数的总和 [英] Output sum of even numbers between two integers

问题描述

我正在我的一门大学课程中研究一个简单的 JAVA 问题.我被这个程序难住了.我将展示我目前所拥有的，并给出我必须回答的问题.我也在 StackOverflow 上查看了一个类似的问题，但这不是同一个问题，所以它没有帮助.我需要写的程序是:

I am working on a simple JAVA question in one of my college courses. I am stumped on this one program. I will display what I have so far and give the question I have to answer. I also looked at a similar question on StackOverflow, BUT it isn't the same problem so it DIDN'T help. The program I need to write is:

编写一个使用while"循环执行以下步骤的程序:

Write a program that uses 'while' loops to perform the following steps:

a.) 提示用户输入两个整数:'firstNum' 和 'secondNum'(firstNum 必须小于 secondNum)

a.) Prompt the user to input two integers: 'firstNum' and 'secondNum' (firstNum must be less than secondNum)

b.) 输出 'firstNum' 和 'secondNum' 之间的所有奇数.

b.) Output all the odd numbers between 'firstNum' and 'secondNum' inclusive.

c.) 输出 'firstNum' 和 'secondNum' 之间所有偶数的总和.

c.) Output the sum of all the even numbers between 'firstNum' and 'secondNum' inclusive.

这就是我目前所拥有的......(我仍然需要计算偶数并将它们相加)

This is what I have so far... (I still need to calculate the even numbers and sum them up)

//import classes
import java.util.*;

public class chapter5no9
{
    static Scanner console = new Scanner(System.in);

    public static void main(String[] args)
    {

    //Part A
    int firstNum;
    int secondNum;
    int sumEven;

    System.out.println("Please enter an integer: ");
    firstNum = console.nextInt();

    System.out.println("Please enter another integer less than the first integer: ");
    secondNum = console.nextInt();

    //Part B
    if (firstNum < secondNum)
    {
        System.out.print("Your second number is greater than the first.  So Please re-enter: ");
        secondNum = console.nextInt();
    }
    else
    {
        System.out.print("Odd Numbers: ");
        firstNum++;
        while (firstNum > secondNum)
        {
            if (secondNum % 2 != 0)
            {
                System.out.print(" " + secondNum);
            }
            secondNum++;
        }

        System.out.println();
        System.out.print("Sum of Even Numbers: ");
        firstNum++;
        while (firstNum > secondNum)
        {
            if (secondNum % 2 != 0)
            {
                System.out.print(" " + secondNum);
            }
            secondNum++;
        }
    }
}

}

推荐答案

我创建了 loopCounter 变量来处理所需的迭代，而无需更改用户输入的值.对您的代码进行了以下更改.

I created the loopCounter variable to handle the required iterations without changing the values inputted by the user. The following changes have been made to your code.

A 部分:添加了一个 while 循环来验证用户输入.还更改了 if 语句中的逻辑.

Part A: added a while loop to validate user input. Also changed logic in if statement.

B 部分:用一个循环打印奇数和总偶数

Part B: used one loop to print odd numbers and total even numbers

   //Part A
   int firstNum;
   int secondNum;
   int sumEven=0;

   System.out.println("Please enter an integer: ");
   firstNum = input.nextInt();

   System.out.println("Please enter another integer less than the first integer: ");
   secondNum = input.nextInt();

   //Part B

   //validate input in a loop
   while(true)
   {
     if (firstNum > secondNum)
     {
         System.out.print("Your second number is larger than the first.  So Please re-enter: ");
         secondNum = input.nextInt();
     }
     else
     {
         break;
     }
   }

       System.out.print("Odd Numbers: ");
       int loopCounter=firstNum;
       while(loopCounter<secondNum)
       {
         if (loopCounter%2!=0)
         {
             System.out.print(" " + loopCounter);
         }//end if
         else
         {
             sumEven+=loopCounter;
         }//end else
         loopCounter++;
       }

       System.out.println();
       System.out.print("Sum of Even Numbers: ");    
       System.out.print(sumEven);

   }

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