Oracle deletes the current connection user __oracle

This is often the case when you use Pl/sql developer to remove users.
"Unable to delete the currently connected user"

Workaround I post the SQL statement directly

   /*
     Delete the current connection user
    * *-
1, first switch to SYSTEM user
-2, query the corresponding SID, serial# of the user processes. -
     Note: The username here must be capitalized
      SELECT sid,serial#,username from v$session WHERE username = ' TEST1 ';
--3, according to the above query results, the user occupies all the process of killing. -
      Note: Sid and Serial# are one by one corresponding
      ALTER SYSTEM KILL session ' xxx, xxx ';
--4, delete user
      test1 CASCADE;