Question

I am trying to generate a regular expression match in Java, that accepts all numbers that contain 3 and 7 (in any order, ie there should be at least one 7 for all 3’s and vice versa) over the set of integers. So far, I have written the code below, however I am not able to get the correct output. Any kind of help will be appreciated:

class Main {
  public static void main (String[] args) throws java.lang.Exception {
    System.out.println("333333".matches("[[3][7]+]*") ? "Yes" : "No");
  }
}

Here, I should be getting the output as NO, since the given string is only of 3’s not of 3 and at least one 7.

Answer 1

I’m not sure if a regex is necessary. Why not use the following:

public static boolean containsDigit(int n, int digit) {
    return String.valueOf(n).contains(String.valueOf(digit));
}

...

int n = 333333;
boolean nContains3And7 = containsDigit(n, 3) && containsDigit(n, 7);