如何将文本文件转换为2D字符数组？

Question

I am trying to convert a text file into a 2 dimensional character array. I am part of the way there but the last line of my array is not fully correct. Here's my code:

protected void readMap(String fileName) throws IOException {
    BufferedReader br = new BufferedReader(new FileReader(fileName));
    char[] chars;
    int lines=0;
    while (br.readLine() != null) {
        lines++;
    }
    File file = new File(fileName);
    try (FileReader reader = new FileReader(file)) {
        chars = new char[(int) file.length()];
        reader.read(chars);
        reader.close();
    } catch (IOException e) {
    }

    int columns = ((int) file.length())/lines;     

    map = new char[lines][columns];
    for(int i=0; i<lines;i++){
        for(int j=0;j<columns;j++){
           map[i][j] = chars[j%columns+i*columns];
        }
    }

    for(int ro=0; ro<map.length; ro++){
                for(int colum=0; colum<(map[0].length); colum++){
                    System.out.print(map[ro][colum]);
                }
            }
    return null;
    }

Here's the output:

##########################
#........................#
#.....###........###.....#
#......G..........G......#
#........................#
#...........E............#
#......G.........G.......#
#........G.....G.........#
#..........###...........#
#........................# 
#################
                 ^missing #'s here

I'm very confused on why this is occuring. I've tried changing how I print the array but i'm pretty sure its how its to do with how i've converted the 1d 'chars' array to the 2d 'map' array. I'm really lost so any help would be much appreciated! Thank you.

Answer 1

I've just executed the code and the map prints as expected. The issue may be down to the file itself as that is the uncommon factor.

edit: The results you have observed is because you may have a new line character, or other special character, at the end of or somewhere in the file. Removing this you should see the consistent map you want.

Alternative

protected static void readMap(String fileName) throws IOException {
    BufferedReader br = new BufferedReader(new FileReader(fileName));
    String line = "";
    List<String> lines = new ArrayList<>();
    while ((line = br.readLine()) != null) {
        lines.add(line);
    }

    char[][] chars = new char[lines.size()][];
    for (int col = 0; col < lines.size(); col++) {
        for (int row = 0; row < lines.get(col).length(); row++) {
            chars[col] = lines.get(col).toCharArray();
        }
    }

    for (int col = 0; col < chars.length; col++) {
        for (int row = 0; row < chars[col].length; row++) {
            System.out.print(chars[col][row]);
        }
        System.out.println();
    }
}//My rows and cols may be back to front

Few other notes:

1. You shouldn't be returning a value from a void method, even null (You'll want to return null if the return type is Void).
2. Your compiler may complain if you don't initialize chars initially, as mine did. char[] chars = null; would do it in this scenario.

Answer 2

I'm guessing your file looks something like this

##########################
#........................#
#.....###........###.....#
#......G..........G......#
#........................#
#...........E............#
#......G.........G.......#
#........G.....G.........#
#..........###...........#
#........................#
##########################

If you print the file length, you will see that the file length is 296

As Your code row = 11 and columns = 26

When you are copying to map you are copying up to 11 * 26 = 286

Try the UPDATED code below

public void readMap(String fileName) throws IOException {
    BufferedReader br = new BufferedReader(new FileReader(fileName));
    int lines = 0, columns = 0;
    String str;
    List<String> lineList = new ArrayList<>();
    while ((str = br.readLine()) != null && str.length() != 0) {
        lines++;
        columns = Math.max(columns, str.length()); // as it's not fixed
        lineList.add(str);
    }
    System.out.println("Row : " + lines);
    System.out.println("Columns : " + columns);

    char[][] map = new char[lines][columns];
    for (int i = 0; i < lines; i++) {
        String currentLine = lineList.get(i);
        int idx = 0;
        for (int j = 0; j < currentLine.length(); j++) {
            map[i][j] = currentLine.charAt(idx++);
        }
    }
    for (int r = 0; r < map.length; r++) {
        for (int c = 0; c < (map[0].length); c++) {
            System.out.print(map[r][c]);
        }
        System.out.println();
    }
}