如何从用户输入列表中添加数字？[副本]

Question

我试图编写一个程序，它会告诉你：

null

import java.util.Scanner;

public class InputParser
{
   public static void main(String[] args)
   {
      Scanner scanner = new Scanner(System.in);
      System.out.print("How many values do you want to parse?: ");
      int numValues = scanner.nextInt();
      System.out.println("Please enter " + numValues + " values: ");

      while(scanner.hasNextLine())
      {
         if(scanner.hasNext())
         {
            if(scanner.hasNextInt())
            {
               int sum;

               System.out.println("The sum of your values is: " + sum + ".");
            }
         }  
         scanner.close();
      }
   }
}

Answer 1

我不明白为什么你会问用户他们想提前和多少个数字。基本上，您的代码可以简化并处理任意数量的数字。在扫描程序包装系统上调用close()也是一个非常糟糕的主意。不管怎样，你可以做一些事情，

Scanner scanner = new Scanner(System.in);
// System.out.print("How many values do you want to parse?: ");
// int numValues = scanner.nextInt();
System.out.println("Please enter values to sum (type quit to stop)");
int sum = 0; // <-- start at 0.
int count = 0;
while (scanner.hasNext()) {
    if (scanner.hasNextInt()) {
        count++;
        sum += scanner.nextInt();
    } else {
        String str = scanner.next();
        if (str.equalsIgnoreCase("quit")) {
            break; // <-- end the loop.
        }
        System.out.printf("The value '%s' is not an int (quit to stop).%n", str);
    }
}
System.out.printf("The sum of your %d values is %d.%n", count, sum);
// scanner.close(); // <-- Really Bad Idea

根据您的评论进行编辑，

Scanner scanner = new Scanner(System.in);
System.out.println("Please enter values to sum (type quit to stop)");
while (scanner.hasNextLine()) {
    String str = scanner.nextLine();
    str = (str != null) ? str.trim() : "";
    if (str.equalsIgnoreCase("quit")) {
        break; // <-- end the loop.
    } else if (str.length() == 0) {
        continue;
    }
    int sum = 0; // <-- start at 0.
    int count = 0;
    Scanner scan2 = new Scanner(str);
    while (scan2.hasNextInt()) {
        count++;
        sum += scan2.nextInt();
    }
    System.out.printf("The sum of your %d values is %d.%n", count, sum);
}