connect via sqlplus and execute:
set heading off
set pagesize 0
set feedback off
set timing off
set time off
set trimspool on
set trimout on
set linesize 100
set echo off
spool t
select 'drop '||object_type||' '||object_name||
decode(object_type,'CLUSTER',' including tables cascade constraints',
'OPERATOR', ' force',
'TABLE',' cascade constraints',
'TYPE', ' force',
'VIEW',' cascade constraints',
'')||';'
from user_objects
where object_type in ('CLUSTER', 'CONTEXT', 'DATABASE LINK', 'DIMENSION',
'DIRECTORY', 'FUNCTION', 'INDEX TYPE', 'JAVA',
'LIBRARY', 'MATERIALIZED VIEW', 'OPERATOR',
'OUTLINE', 'PACKAGE', 'PROCEDURE', 'SEQUENCE',
'SYNONYM', 'TABLE', 'TYPE', 'VIEW')
order by object_type, object_name
/
spool off
@t.lst
purge recyclebin;