如何在java中从控制台获取数字？

Question

这是我的方法，如果我想从用户那里得到一个数字，就会调用它。但是，如果用户也输入了正确的数字，那么“else”部分就会运行，为什么

你能解释一下吗

    public static int chooseTheTypeOfSorting() {
    System.out.println("Enter 0 for merge sorting OR enter 1 for bubble sorting");
    int numberFromConsole = 0;
    try {
        InputStreamReader isr = new InputStreamReader(System.in);
        BufferedReader br = new BufferedReader(isr);
        String s = br.readLine();
        DecimalFormat df = new DecimalFormat();
        Number n = df.parse(s);
        numberFromConsole = n.intValue();

    } catch (ParseException ex) {
        Logger.getLogger(DoublyLinkedList.class.getName()).log(Level.SEVERE, null, ex);
    } catch (IOException ex) {
        Logger.getLogger(DoublyLinkedList.class.getName()).log(Level.SEVERE, null, ex);
    }
    return numberFromConsole;
}

在我的主要方法中：

 public static void main(String[] args) {
    int i = 0;
    i = getRandomNumber(10, 10000);
    int p = chooseTheTypeOfSorting();
    DoublyLinkedList list = new DoublyLinkedList();
    for (int j = 0; j < i; j++) {
        list.add(j, getRandomNumber(10, 10000));

        if (p == 0) {
           //do something....
        }
        if (p == 1) {
            //do something.....
        } else {
            System.out.println("write the correct number ");
            chooseTheTypeOfSorting();
        }