Hello Friends, How are you? Today I am going to solve the HackerRank Java Valid Username Regular Expression Problem with a very easy explanation. This is the 23rd problem of Java on HackerRank. In this article, you will get more than one approach to solving this problem. So let’s start- {tocify} $title={Table of Contents} 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 8 or greater than 30 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].
| Username | Validity |
|---|---|
| Julia | INVALID; Username length < 8 characters |
| Samantha | VALID |
| Samantha_21 | VALID |
| 1Samantha | INVALID; Username begins with non-alphabetic character |
| Samantha?10_2A | INVALID; ‘?’ character not allowed |
Update the value of regularExpression field in the UsernameValidator class so that the regular expression only matches with valid usernames. The first line of input contains an integer n, describing the total number of usernames. Each of the next n lines contains a string describing the username. The locked stub code reads the inputs and validates the username.
- The username consists of any printable characters.
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