Exception occured when connecting java to oracle 10g -

my code below.

java.sql.drivermanager.registerdriver(new oracle.jdbc.driver.oracledriver()); java.sql.connection con=drivermanager.getconnection("jdbc:oracle:thin:@localhost:1521:xe", "ims", "_ims"); 

the exception occurs @ second line given below.

java.sql.sqlexception: listener refused connection following error: ora-12505, tns:listener not know of sid given in connect descriptor connection descriptor used client was: localhost:1521:xe" 

what exception means? whats wrong in code?

edit girish

the listener.ora file :

sid_list_listener =   (sid_list =     (sid_desc =       (sid_name = plsextproc)       (oracle_home = c:\oraclexe\app\oracle\product\10.2.0\server)       (program = extproc)     )     (sid_desc =       (sid_name = clrextproc)       (oracle_home = c:\oraclexe\app\oracle\product\10.2.0\server)       (program = extproc)     )   )  listener =   (description_list =     (description =       (address = (protocol = ipc)(key = extproc_for_xe))       (address = (protocol = tcp)(host = girish-pc)(port = 1521))     )   )  default_service_listener = (xe) 

the tnsnames.ora file :

xe =   (description =     (address = (protocol = tcp)(host = girish-pc)(port = 1521))     (connect_data =       (server = dedicated)       (service_name = xe)     )   )  extproc_connection_data =   (description =     (address_list =       (address = (protocol = ipc)(key = extproc_for_xe))     )     (connect_data =       (sid = plsextproc)       (presentation = ro)     )   )  oraclr_connection_data =    (description =      (address_list =        (address = (protocol = ipc)(key = extproc_for_xe))      )      (connect_data =        (sid = clrextproc)        (presentation = ro)      )    )  

in above, both tnsnames.ora , listener.ora file's contents given.

i've replaced oracle**.jar new one, n work. think there problem old oracle**.jar. support.