Question

我一直试图让这个程序工作，它应该继续从用户那里获取输入，直到输入-1并计算总和。问题如下：设计并实现一个Java程序（命名它 InputSum ）提示用户输入正整数。该计划应该是ac cept整数，直到用户输入值-1 （否定的）。用户输入-1后，程序s 应显示输入的数字，然后显示其总和如下所示。请注意，-1不是输出的一部分。确保程序在proc之前验证每个输入的数字因为用户可能输入负数句子值以外的数字-1 。
设计你的程序就好了允许用户重新运行程序在同一次运行中使用不同的输入集，如上所示。记录您的代码，并组织和如上所示，将输出空间化。

这是我的代码：

/* Class:        CS1301
* Section:       9:30
* Term:          Fall 2015
* Name:          Matthew Woolridge
* Instructor:    Mr. Robert Thorsen
* Assignment:    Assignment 6
* Program:       1
* ProgramName:   InputSum
* Purpose:       The program prompts the user to input numbers until -1 is entered and calculates the sum
* Operation:     The information is statically instantiated in the code and
*                the data is output to the screen.
* Input(s):      The input is the numbers
* Output(s):     The output will be the sum of the numbers
* Methodology:   The program will use loops to determine if numbers or still to be entered or if -1 was entered
*
*/

import java.util.*;
import java.io.*;
public class InputSum
{

   public static void main (String[] args)
   {

      /******************************************************************************
      *                          Declarations Section                               *
      ******************************************************************************/
      /****************************CONSTANTS********************************/
      Scanner scan = new Scanner(System.in); //Initializes scanner

      int n = 1;
      int [] num = new int[n]; //Creates array for input numbers
      int i;
      int sum=0;

      /******************************************************************************
      *                             Inputs Section                                  *
      ******************************************************************************/

      System.out.print("Please input integers, note that -1 ends the submissions: "); //Prompts the user for input

     /****************************variables********************************/
     //***************************Calculations in processing************************//
     /******************************************************************************
      *                             Processing Section                            *
      ******************************************************************************/
      for(i=0; i<num.length; i++)
      {
         num[i] = scan.nextInt(); //Continues to read numbers and add them to the sum
         n = n + 1; //Adds to the array maximum
         sum = sum + num[i]; //Calculates the sum
         if (num[i] == -1){
            break;
         }
      }
      System.out.print("The numbers entered are: " + num[i]);
      System.out.print("\nThe sum of the numbers is: " + sum);

      /******************************************************************************
       *                              Outputs Section                                *
       ******************************************************************************/
       //***************Output is in the processing**************************//
   }
}

问题是，程序一直挂在应该打印总和的行上。任何和所有的帮助表示赞赏！

Answer 1

您可以使用临时变量来计算总和的值，而不是使用数组（因为它限制了输入的数量）。如下图所示：

int sum=0;
int num=0;
while(num != -1) {
    sum = sum + num;
    num = scan.nextInt(); //note that the variables can be reused
}

Answer 2

您可以使用List来存储数字和无限循环以保持接收来自用户的输入。此外，您应该在开始处理数字之前检查停止条件（因为您的问题提到-1不是输出的一部分）。这是一个例子

import java.util.*;
import java.io.*;
public class InputSum
{

   public static void main (String[] args)
   {

      /******************************************************************************
      *                          Declarations Section                               *
      ******************************************************************************/
      /****************************CONSTANTS********************************/
      Scanner scan = new Scanner(System.in); //Initializes scanner
      int number; //Declare a variable that will hold the temporal value that is read on the input stream      
      int sum=0;

      // Use a List 
      List<Integer> numbers = new ArrayList<Integer>();

      /******************************************************************************
      *                             Inputs Section                                  *
      ******************************************************************************/

      System.out.print("Please input integers, note that -1 ends the submissions: "); //Prompts the user for input

     /****************************variables********************************/
     //***************************Calculations in processing************************//
     /******************************************************************************
      *                             Processing Section                            *
      ******************************************************************************/
      // use an infinite loop
      for(; ; )
      {


         // You should normally do this check when you enter the loop
         // so that -1 which is a stop token should not be added to the list
         // and not taken into account in the sum


         number = scan.nextInt(); //Continues to read numbers and add them to the sum
         if (number == -1){
              break;
         }

         // You could write numbers.add(number) which would be
         // Java's autoboxing feature, but this is what would really take place
         numbers.add(Integer.valueOf(number));
         sum += number; //Calculates the sum


      }
      System.out.print("The numbers entered are: " + numbers);
      System.out.print("\nThe sum of the numbers is: " + sum);

      /******************************************************************************
       *                              Outputs Section                                *
       ******************************************************************************/
       //***************Output is in the processing**************************//
   }
}

无法弄清楚程序无法正常运行的原因

2 个答案: