java - 输出两个整数之间偶数的和

Question

我正在研究我的一门大学类(class)中的一个简单的 JAVA 问题。我对这个程序感到困惑。我将展示我目前所拥有的，并给出我必须回答的问题。我还在 StackOverflow 上查看了一个类似的问题，但它不是同一个问题，所以它没有帮助。我需要编写的程序是:

编写一个使用“while”循环执行以下步骤的程序:

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

b.) 输出'firstNum'和'secondNum'之间的所有奇数。

c.) 输出'firstNum'和'secondNum'之间所有偶数的和。

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)

//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++;
        }
    }
}

}

Answer 1

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

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。

B部分:用一个循环打印奇数和总偶数

   //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);

   }