Java扫描仪例外java.util.NoSuchElementException

Question

Hello I have a problem reading integer values from scanner. Program sorts two arrays and saves the sorted values into new array and then it writes it on the console output. Here is exception:

Exception in thread "main" java.util.NoSuchElementException
at java.util.Scanner.throwFor(Unknown Source)
at java.util.Scanner.next(Unknown Source)
at java.util.Scanner.nextInt(Unknown Source)
at java.util.Scanner.nextInt(Unknown Source)
at U42Slevani.main(U42Slevani.java:40)

Here is my code.

package u42slevani;
import java.util.Scanner;



/**
 *
 * @author matej.rehak
 */
public class U42Slevani {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here
        Scanner sc = new Scanner(System.in);
        int[] pole1;
        int[] pole2;
        int pocet=1;


        while(pocet>0)
        {

            int pom;
            int j;



        pocet = sc.nextInt();
        if(pocet<0 || pocet>1000)
        {
            break;
        }
        pole1 = new int[pocet];
        for(int i = 0;i<pole1.length;i++)
        {
            pole1[i] = sc.nextInt();
        }

        pocet = sc.nextInt();   //problem here

        if(pocet<0 || pocet>1000)
        {
            break;
        }
        pole2  = new int[pocet];
        for(int i = 0;i<pole2.length;i++)
        {
            pole2[i] = sc.nextInt();
        }

            for (int i = 1; i<pole1.length; i++)
            {
                pom = pole1[i];
                j = i - 1;
                while ((j >= 0 ) && (pole1[j] > pom))
                {
                    pole1[j+1] = pole1[j];
                    j--;
                }
                pole1[j+1] = pom;
            }

            for (int i = 1; i<pole2.length; i++)
            {
                pom = pole2[i];
                j = i - 1;
                while ((j >= 0 ) && (pole2[j] > pom))
                {
                    pole2[j+1] = pole2[j];
                    j--;
                }
                pole2[j+1] = pom;
            }

            int[] pole3 = new int[pole1.length+pole2.length];
            merge(pole3, pole1, pole2);
            StringBuilder vystup = new StringBuilder("");
            for (int i = 0; i < pole3.length - 1; i++) 
            {
                vystup.append(pole3[i] + " ");
            }
            vystup.append(pole3[pole3.length -1]);
            System.out.println(vystup);


        }
    }

  public static void merge(int[] list, int[] left, int[] right) {
  int i = 0;
  int j = 0;
  // dokud nevyjedeme z jednoho z poli
  while ((i < left.length) && (j < right.length)) {
    // dosazeni toho mensiho prvku z obou poli a posunuti indexu
    if (left[i] < right[j]) {
      list[i + j] = left[i];
      i++;
    }
    else {
      list[i + j] = right[j];
      j++;
    }
  }
  // doliti zbytku z nevyprazdneneho pole
  if (i < left.length) {
    while (i < left.length) {
      list[i + j] = left[i];
      i++;
    }
  }
  else {
    while (j < right.length) {
      list[i + j] = right[j];
      j++;
    }
  }
}

}

I know problem is on line 41 but I don't know why. Thank you.

Answer 1

You are trying to read the next integer from the underlying stream of the Scanner by calling nextInt() , even though you are not sure there is something to be read. If you try to read the next integer when there is none to be read, a NoSuchElementException will be thrown.

Solve this by first checking if there is an integer to be read, and in that case read it.

if(sc.hasNextInt()) 
{
   pocet = sc.nextInt();
}