public class ParseInt {
    public static int parse(String str) {
        if (str.isEmpty()) {
            return 0;
        }

        int num = 0;

        switch (str.charAt(0)) {
            case '1' :
                num = 1;
                break;
            case '2' :
                num = 2;
                break;
            case '3' :
                num = 3;
                break;
            case '4' :
                num = 4;
                break;
            case '5' :
                num = 5;
                break;
            case '6' :
                num = 6;
                break;
            case '7' :
                num = 7;
                break;
            case '8' :
                num = 8;
                break;
            case '9' :
                num = 9;
                break;
        }

        return num * (int) Math.pow(10, str.length() - 1) + parse(str.substring(1));
    }
}