in auth/src/main/java/com/google/firebase/quickstart/AuthSnippets.java [37:43]
public static void getUserByEmail(String email) throws InterruptedException, ExecutionException {
// [START get_user_by_email]
UserRecord userRecord = FirebaseAuth.getInstance().getUserByEmailAsync(email).get();
// See the UserRecord reference doc for the contents of userRecord.
System.out.println("Successfully fetched user data: " + userRecord.getEmail());
// [END get_user_by_email]
}