扫描程序仅读取文本文件的第一行

Question

This is my code

    public static void main(String[] args) {

    File source = //


    Scanner s = null;       
    int lineNumber =0;
        ArrayList<ArrayList<Integer>> tagsArray = new ArrayList<>();
    try {

        s= new Scanner(source);
    while (s.hasNext()) {

            String[] cols = s.nextLine().split("    ");

            for (int i = 0; i < cols.length; i++) {
                if (cols[i].equals("1"))
                    tagsArray.get(i).add(lineNumber);
                }
            lineNumber++;

        }   
    } catch (Exception e) {
        // TODO: handle exception
    }
}

When I delete the for statement it read the whole text file but when I use it it read only the first line why?

Answer 1

I guess you get an Exception , but you catch and hide it instead of handling it. This is very bad! You should at least print the stacktrace of the exception.

You try to access:

tagsArray.get(i).add(lineNumber);

when tagsArray is empty. You need to instantiate each ArrayList<Integer> inside tagsArray before accessing it.