JRJC: Getting User's Display Name from the User ID

Does anyone know the easiest way to get the current user’s Display name using JRJC (Java REST Jira Client) or JS?

Currently I was able to get the user’s ID from the AP javascript function helper with the following code:

AP.user.getCurrentUser(function(user) {
        currentUserId = user.atlassianAccountId;
        console.log("The Atlassian Account ID is", currentUserId);
    });

Now that I have the ID of the current user, I have passed it back to Springboot to have the Java REST Jira Client attempt to use the ID to find the current user’s display name, but I’m having a hard time trying to find the correct path forward here.

Any help?

Ty in advance!