Java : Error when reading input with BufferedReader

Question

I'm working with Java to interpret some input. And I'm using BufferedReader. My goal is to read an amount number of lines after reading a char, where -1 is the stop command. Something like this

2
CASE 1 - L1
CASE 1 - L2
3
CASE 2 - L1
CASE 2 - L2
CASE 2 - L3
-1

My goal would be have as an output just :

CASE 1 - L1
CASE 1 - L2
CASE 2 - L1
CASE 2 - L2
CASE 2 - L3

What would mean that I'm getting the lines in the right way. My code is as follows:

public class TESTE {

    public static void main(String[] args) throws IOException {
        BufferedReader buffer = new BufferedReader(new InputStreamReader(System.in));
        int state;

        while ((state = buffer.read()) != 45) {
            char c = (char) state;
            if (Character.isDigit(c)) {
                int n = Character.getNumericValue(c);
                for (int i = 0; i < n; ++i) {
                    System.out.println("L:" + buffer.readLine());
                    System.out.println();
                }
            }
        }

    }

}

For some reason my output is:

L:
L:CASE 1 - L1
L: - L2
L:
L:CASE 2 - L1
L:CASE 2 - L2
L: - L3

What am I doing wrong ? Is there an elegant way to deal with that Input ?

Answer 1

Here's what happened.

1. buffer.read() returns 50 which is '2'
2. Convert it to n, which is 2
3. Read two lines

Now what's next in the buffer at this point? A \n right after '2'! That's why you get your first output

L:

An Empty Line.

Well there's no point to continue. The whole process is broken.

One way to do it:

    Scanner in = new Scanner(System.in);
    while (true) {
        int n = Integer.parseInt(in.nextLine());
        if (n == -1) break;
        for (int i = 0; i < n; i++) {
            System.out.println("L:" + in.nextLine());
        }
    }