When transforming email addresses into usernames, which syntax is correct?

When transforming email addresses into usernames, using the syntax String.substringBefore("jsmith@oktaice.com", "@") successfully extracts the portion of the string that comes before the "@" symbol. This is the desired outcome when converting an email to a username, as usernames typically do not include the domain part of an email address.

The substringBefore method is specifically designed to return the substring that occurs before the specified delimiter, which in this case is the "@" character. Therefore, applying this method will yield "jsmith", which is precisely the username portion of the email address.

In contrast, the other options either yield the wrong part of the string or do not conform to the expected syntax for extracting elements from a string. For example, using substringAfter would return the string that appears after the "@" symbol, which is not what is needed for this transformation. Similarly, the extractBefore method is not a standard string manipulation function found in typical programming contexts, and while split can achieve the desired result, it requires additional indexing to isolate the username. Thus, the most straightforward and correct approach for this scenario is to use the substringBefore method as indicated in the correct answer.