String regularExpression = ^1-9d5181920d201-91011120-21-910203031d30-9Xx$ + ^1-9d5d201-91011120-21-910203031d3$;

This regular expression is used to validate Chinese ID card numbers.

The first part of the regular expression, "(^[1-9]\d{5}(18|19|20)\d{2}((0[1-9])|(10|11|12))(([0-2][1-9])|10|20|30|31)\d{3}[0-9Xx]$)", matches the 18-digit ID card number format.

• The first digit must be a number between 1-9.
• The next 5 digits represent the birthplace code.
• The next 4 digits represent the birth year.
• The next 2 digits represent the birth month.
• The next 2 digits represent the birth day.
• The next 3 digits represent the sequence code.
• The last digit can be either a number between 0-9 or the letter X (or x) to represent a check code.

The second part of the regular expression, "(^[1-9]\d{5}\d{2}((0[1-9])|(10|11|12))(([0-2][1-9])|10|20|30|31)\d{3}$)", matches the 15-digit ID card number format.

• The first digit must be a number between 1-9.
• The next 5 digits represent the birthplace code.
• The next 2 digits represent the birth year.
• The next 2 digits represent the birth month.
• The next 2 digits represent the birth day.
• The last 3 digits represent the sequence code.

Overall, this regular expression ensures that the ID card number provided follows the correct format and contains valid birthplace, birth date, and sequence code information