我的循环怎么了？ 不断收到NoSuchElementException

Question

I keep getting a NoSuchElement Exception at the line maze[r][c]=scan.next(); . How can I resolve that?

  try {
        Scanner scan = new Scanner(f);
        String infoLine = scan.nextLine();
        int rows=0;
        int columns=0;
        for(int i = 0; i<infoLine.length();i++){
            if(Character.isDigit(infoLine.charAt(i))==true){
                rows = (int)infoLine.charAt(i);
                columns = (int)infoLine.charAt(i+1);
                break;
            }
        }

        String [][] maze = new String[rows][columns];
        int r = 0;
        while(scan.hasNextLine()==true && r<rows){
            for(int c = 0; c<columns;c++){
                maze[r][c]=scan.next();
            }
            r++;
        }
        return maze;
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }

Answer 1

Look at this part of your code:

    while(scan.hasNextLine()==true && r<rows){  // 1
        for(int c = 0; c<columns;c++){          // 2
            maze[r][c]=scan.next();             // 3
        }                                       // 4
        r++;                                    // 5
    }                                           // 6

In line 1 you are checking to make sure that scan has another line available. But in line 3, you read that line - inside the 2:4 loop. So if there are more than 1 columns, you will be asking for the next scan more than once - and you only checked to see if there was one next line. So on the second column, if you're at the end of scan, you try to read from scan even though it's run out.

Try this:

try {
    Scanner scan = new Scanner(f);
    String infoLine = scan.nextLine();
    int rows = 0;
    int columns = 0;
    for (int i = 0; i < infoLine.length();i++) {
        if (Character.isDigit(infoLine.charAt(i))) {
            rows = Character.digit(infoLine.charAt(i), 10);
            columns = Character.digit(infoLine.charAt(i + 1), 10);
            break;
        }
    }

    String [][] maze = new String[rows][columns];
    int r = 0;
    while(scan.hasNextLine() && r < rows) {
        int c = 0;
        while(scan.hasNextLine() && c < columns) {
            maze[r][c]=scan.next();
            c++
        }
        r++;
    }
    return maze;
} catch (FileNotFoundException e) {
    e.printStackTrace();
}