Valid Username Regular Expression
Valid Username Regular Expression: Problem Description: You are updating the username policy on your company's internal networking platform. According to the policy, a username is considered valid if all the following constraints are satisfied: The username consists of 8 to 30 characters inclusive. If the username consists of less than or greater than 8 characters, then it is an invalid username. The username can only contain alphanumeric characters and underscores (_). Alphanumeric characters describe the character set consisting of lowercase characters[a-z] , uppercase characters[A-Z] , and digits[0-9]. The first character of the username must be an alphabetic character, i.e., either lowercase character [a-z] or uppercase character [A-Z]. Update the value of regularExpression field in the UsernameValidator class so that the regular expression only matches with valid usernames. Input Format The first line of input contains an integer , describing the total number of usernames. Ea...