public class Task2 {
    public static void main(String[] args) {
        System.out.println(count7(71)); // 5
    }

    private static int count7(int number) {
        int j = 0;
        int counter = 0;
        String strNumber = Integer.toString(number);
        int i = strNumber.length();

        if (j == i) {
            return counter;
        }

        if (strNumber.startsWith("7")) {
            System.out.println(strNumber.substring(0, 1));
            counter++;
        }
        String substring = strNumber.substring(j + 1, i);
        int recur = count7(Integer.parseInt(substring));
        return counter + recur;
    }
}

import java.util.regex.*;

class Task2 {
    public static void main(String[] args) {
        String seven = "1227442723237477";
        Pattern pattern = Pattern.compile("7");
        Matcher matcher = pattern.matcher(seven);

        int count = 0;
        while (matcher.find())
            count++;

        System.out.println(count);    // 5
    }
}