Java prepared statement returns incorrect results

Hi this is really an oracle question but because I'm doing the work in java (response times are java queries are cool), I thought I'd post the question here!

basically I have a oracle table as defined below.

CREATE TABLE INSTRUMENT
(
  INSTID              NUMERIC(10)     ,  (key field)
  CCY                 CHAR(3)             ,    
  PRICINGBASIS        NUMERIC(28,14)           ,
  INSTRUMENTCLASS     VARCHAR(20)         ,
  INSTRUMENTSUBCLASS  VARCHAR(20)        ,

)  APRROX 14 000  rows

I also have another oracle table INSTRUMENT_TEMP (approx 400 rows)  with the same table definition. This table brings
in new instruments every day but has some old instruments which will already be in INSTRUMENT.

I need to insert all data rows in  INSTRUMENT_TEMP which do not exists in INSTRUMENT ie all instid that are not there.

I'm doing this in a prepared statement, the java looks ok (has been checked by others) I just need to get the ORACLE
right .

When I do my query I end up with all the rows which are in INSTRUMENT and not in INSTRUMENT_TEMP!
but I'm interested in those which are in INSTRUMENT_TEMP but not in INSTRUMENT.

So if  INSTRUMENT_TEMP has 400 rows (INSTRUMENT has 14000) of which 100 are new my query should return 100 rows , I get
13900 rows in my resultset !

INSERT INTO INSTRUMENT
SELECT it.instind,
           it.....
FROM INSTRUMENT i,
         INSTRUMENT_TEMP it
WHERE it.instid != i.inst_id

Please help!