If you open the "System Settings" app, there's an icon in the top row for something like "application settings" (I think it's second or third from the left in the top row--I don't have KDE available at the moment). If you click on that icon you'll see a dialogue with a few options in the left-hand panel. One of them is to set the theme for GTK applications. You should just be able to select qtcurve from the drop-down menu in the right-hand pane under that tab.
Best Answer
You can try to set Java's default look and feel to GTK:
Open a terminal ( Ctrl + Alt + T ) and paste the upper one for openjdk and the lower one for sun java .
gksu gedit /usr/lib/jvm/java-6-openjdk/jre/lib/swing.propertiesgksu gedit /usr/lib/jvm/java-6-sun/jre/lib/swing.propertiesFollow the comment in that file and remove the hash sign, so it looks like:
Save and restart the java app.
Before and after: