Validates the number expected commas in a CSV

CsvValidator.java

  /**
   * Validate row of csv to see if it has the correct number of commas.
   * @param input The csv row to be evaluated.
   * @param expectedNumberOfCommas The expected number of commas in the csv row.
   */
  public static void validateLine(String input, int expectedNumberOfCommas) {
    // Example input: [email protected],Male,21

    // Check that there are 2 commas in the input:
    // regex = ^([^,]*,){2}[^,]*$
    // ^ Start of string
    // ( Start of group
    // [^,]* Any character except comma, zero or more times
    // , A comma
    // ){2} End and repeat the group 2 times only. Eg. if we expect only 2 commas for the line.
    // [^,]* Any character except comma
    // $ End of string
    String regex = "^([^,]*,){" + expectedNumberOfCommas + "}[^,]*$";

    boolean isCsvValid = Pattern.matches(regex, input);

    if (!isCsvValid) {
      throw new RuntimeException(
          "Invalid csv. Expecting " + expectedNumberOfCommas + " comma(s) per line only.");
    }
  }