将文本文件读取到Java中的char [] []数组中

Question

I am trying to fill a char[][] array from a text file and I cannot seem to figure out how to do it. I've tried to use .toCharArray() but it doesn't seem to work. If you can give any insight on how to make this work that would be awesome!

String filename = "ArrayHW2.txt";
        int numTests = 6;
        char[][] testAnswers = new char[50][5];
        char[] key = new char[4];

        Scanner input = null;
        try
        {
            input = new Scanner(new File(filename));
        }
        catch(FileNotFoundException e)
        {
            System.out.println("Error Opening File");
            System.exit(1);
        }

        for(int row = 0; row < testAnswers.length; row++)
        {
            for(int col = 0; col < testAnswers[row].length; col++)
            {
                testAnswers[row][col] = input.next().toCharArray();
            }
        }
        input.close();

Answer 1

The basic problem is that you are trying to assign a character array to something was meant to hold a character. You might think of char[] type as storing the location in memory where characters are recorded, and a char type as the character itself.

When you call toCharArray() on a String , the return type is char[] . It looks like you expect this array to have a single character, like the A, B, C, or D of a multiple-choice test. You could get the first (and only?) character of that array with something like ...toCharArray()[0] , but this is wasteful because a new array is created, and characters are copied into it from the source string. It's simpler to use the getCharAt() method on the String directly.

String filename = "ArrayHW2.txt";
char[][] testAnswers = new char[50][5];
try (Scanner input = new Scanner(Paths.get(filename))) {
  for(int row = 0; row < testAnswers.length; row++) {
    for(int col = 0; col < testAnswers[row].length; col++) {
      String token = r.next();
      if (token.length() != 1)
        throw new IllegalArgumentException("Answers must be one character");
      testAnswers[row][col] = token.charAt(0);
    }
  }
} catch (IOException ex) {
  System.err.println("Error reading file: " + ex.getMessage());
  System.exit(1);
}

Answer 2

String filename = "ArrayHW2.txt";
        int numTests = 6;
        char[][] testAnswers = new char[50][5];
        //char[] key = new char[4];

        Scanner input = null;
        try
        {
            input = new Scanner(new File(filename));
        }
        catch(FileNotFoundException e)
        {
            System.out.println("Error Opening File");
            System.exit(1);
        }
        int counter = 0;
        while(scanner.hasNext())
        {
            copyString(testAnswers[counter], scanner.nextLine());

        }

        input.close();

its been a while i haven't code in java and im not sure about the methods but consider it a pseudo code . you can use this copy :

void copyString(char[] arr, String x)
{
   int size = x.length();
   for (int i=0; i<size; i++){
   arr[i] = x.CharAt(i);
}