Почему при любом количестве символов в текстовом документе последние из них "0"? То есть в другом текстовом документе ставится "пробел"

public class Solution {
    public static void main(String[] args) throws Exception {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

        FileInputStream inputStream = new FileInputStream(reader.readLine());
        FileOutputStream outputStream = new FileOutputStream(reader.readLine());
        byte[] count = new byte[inputStream.available()];
        for (int i = 0; i < inputStream.available(); i++)
        {
            count[i] = (byte) inputStream.read();

        }
        System.out.println(Arrays.toString(count));
        for (int i = inputStream.available(); i >= 0; i--) {
            outputStream.write(count[i]);
        }

        inputStream.close();
        outputStream.close();
    }
}