Regular expression to check if the same char is repeated.

regular_expression_same_char_repeation.java

// 문자열에 반복되는 문자가 있는지 확인
public static boolean checkSameCharRepeated(@NonNull String password, int repeatLength) {

    if (repeatLength <= 1) return false;

    Pattern p = Pattern.compile(".*([a-zA-Z0-9])\\1{"+ (repeatLength - 1) +",}.*");

    return p.matcher(password).matches();

}