java is locked when select for update

Hello,

I use Postgresql 8.0.1 with java 5 and jdbc3 on windows xp.

When I do a "select for update" a row.. and dont commit the statement
and when in this time an other user do also this. my java gui wait and
locked till the first user commit his statement.. my question is how
can I realize this with java.. for example why they are not a
SQLException or are Error like "an other user is updating this row"...
or can I say to java "dont wait" or "dont lock" when you make a select
for update and an other user before you make this..

thank you..

best regards

Mican Bican