java - Java NoSuchElementException

Question

这是我编写的一个简单程序，用于对 txt 文件中的整数进行计算。经过几个小时的尝试调试后，我希望有一双新的眼睛能够发现我的一些问题。编辑:data.txt 包含整数 1-5。每行一个整数。

import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Scanner;

public class Calculator {

public static int[] NUMBERS;    //global value for the array

public static void main(String[] args) throws FileNotFoundException {
    File file = new File("data.txt");
    Scanner sc = new Scanner(file);

    List x = new ArrayList();

    while (sc.hasNextInt()) {
        x.add(sc.nextInt());
    }

    NUMBERS = new int[x.size()];
    Iterator<Integer> iterator = x.iterator();
    for (int i = 0; i < NUMBERS.length; i++) {
        NUMBERS[i] = iterator.next().intValue();
    }

    sc.close();

    Scanner sc2 = new Scanner(file);

    System.out.println("Welcome to Calculation Program!\n");
    startMenus(sc2);

}

private static void startMenus(Scanner sca) throws FileNotFoundException {
    while (true) {
        System.out.println("(Enter option # and press ENTER)\n");

        System.out.println("1. Display the average of the list");
        System.out.println("2. Display the number of occurences of a given element in the list");
        System.out.println("3. Display the prime numbers in a list");
        System.out.println("4. Display the information above in table form");
        System.out.println("5. Save the information onto a file in table form");
        System.out.println("6. Exit");

        int option = sca.nextInt();

        sca.nextLine();

        switch (option) {
            case 1:
                infoMenu1(sca);
                break;
            case 2:
                infoMenu2(sca);
                break;
            case 3:
                infoMenu3(sca);
                break;
            case 4:
                infoMenu4(sca);
                break;
            case 5:
                infoMenu5(sca);
                break;
            case 6:
                System.exit(0);
            default:

                System.out.println("Unrecognized Option!\n");
        }

    }
}

private static void infoMenu1(Scanner sc2) {
    System.out.println("The average of the numbers in the file is: " + avg(NUMBERS));
}

public static double avg(int[] numbers) {
    int sum = 0;

    for (int i = 0; i < numbers.length; i++) {
        sum = (sum + numbers[i]);
    }

    return (sum / numbers.length);
}

public static int occr(int[] numbers, int x) {
    int count = 0;

    for (int n : numbers) {
        if (n == x) {
            count = count + 1;
        }
    }

    return count;
}

public static boolean prime(int x) {
    boolean answer = true;

    if (x == 0 || x == 1) {
        return false;
    }

    for (int i = 2; i <= x / 2; i = i + 1) {
        if (i != x) {
            if (x % i == 0) {
                answer = false;
            }
        }
    }

    return answer;
}

public static int[] primes(int[] numbers) {
    int primesCount = 0;

    for (int i : numbers) {
        if (prime(i)) {
            primesCount = (primesCount + 1);
        }
    }

    if (primesCount == 0) {
        return null;
    }

    int[] result = new int[primesCount];
    int index = 0;

    for (int i : numbers) {
        if (prime(i)) {
            result[index] = i;
            index = index + 1;
        }
    }

    return result;
}

private static void infoMenu2(Scanner sc) {
    sc = new Scanner(System.in);
    System.out.println("Which integer would you like to check for number of occurences?");
    int choice = sc.nextInt();

    System.out.println("The number of occurence(s) of " + choice + " are/is " + occr(NUMBERS, choice));


}

private static void infoMenu3(Scanner sc2) {
    int[] myPrimes = primes(NUMBERS);

    System.out.println("The prime number(s) in the file are/is: ");

    for (int j = 0; j < myPrimes.length; ++j) {
        System.out.println(myPrimes[j] + " ");
    }

}

private static void infoMenu4(Scanner kb) throws FileNotFoundException {
    File file = new File("data.txt");
    Scanner sc = new Scanner(file);

    int counter = 0;
    while (sc.hasNextInt()) {
        counter = counter++;
    }

    int lenth = counter;

    int[] column1 = new int[lenth];
    while (sc.hasNextInt()) {
        column1 = new int[sc.nextInt()];
    }

    int[] column2 = new int[occr(NUMBERS, sc.nextInt())];

    boolean column3 = prime(sc.nextInt());

    System.out.printf("Average: " + "%20.2f", column1);
    System.out.println();
    System.out.printf("Occurences: " + "%14d", column2);
    System.out.println();
    System.out.printf("Primes:" + "%19s : %s", column3);
    System.out.println();
}

private static void infoMenu5(Scanner kb) throws FileNotFoundException {
    File file = new File("data.txt");
    Scanner sc = new Scanner(file);
    PrintWriter pw = new PrintWriter(new File("results.txt"));

    int counter = 0;
    while (sc.hasNextInt()) {
        counter = counter++;
    }

    int lenth = counter;

    int[] column1 = new int[lenth];
    while (sc.hasNextInt()) {
        column1 = new int[sc.nextInt()];
    }

    int[] column2 = new int[occr(NUMBERS, sc.nextInt())];

    boolean column3 = prime(sc.nextInt());

    pw.printf("Number: " + "%-10d", column1);
    pw.println();
    pw.printf("Occurences: " + "%12d", column2);
    pw.println();
    pw.printf("Primes:" + "%24s : %s", column3);
    pw.println();

    pw.close();
}

}

Answer 1

您在代码中使用了错误的扫描仪(第 49 行)。我想您正在尝试获取用户输入。但是，您正在使用 Scanner 从 data.txt 获取输入。

根据评论更新。实际上，您不需要 startMenus 中 data.txt 中的 Scanner。您需要的是用户输入。因此，将 System.in 中的 sc2 更改为 Scanner。

原始第31行:

// Scanner sc2 = new Scanner(file);
Scanner sc2 = new Scanner(System.in);