How to find a locked object in oracle

select a.sid,a.serial#,c.object_name
 from V$session a,
 V$lock b,
 user_objects c
 where a.sid=b.sid
 and b.ID1=c.object_id;

or

select a.sid,a.serial#,c.object_name 
 from V$session a, 
 V$locked_object b, 
 user_objects c 
 where a.sid=b.session_id 
 and b.object_id=c.object_id;

to kill it use the below query

ALTER SYSTEM KILL SESSION 'sid,serial#';