How to run Java application in KDE with Qt-like UI?

Using those Qt bindings is no solution (it requires that the whole application's GUI has to be rewritten).

And OpenOffice.org is written in C++ mostly, with some parts written in other languages like Java. It also has its own GUI toolkit that can mimic Gtk or Qt (partially) using themes.

And if there is no Qt or KDE-like theming included, I have no idea how to make one. (I just saw that there are a couple of additional Swing themes in the repository, that might be a thing to try out for those applications that use Swing.)

One solution is to use some sort of aesthetically Qt-compatible GTK theme, through the java GTK Style look and feel.

In Kubuntu, for GTK applications you can install the Qt Curve theme (qtcurve package), you should then be able to configure the default GTK style in KDE System Settings (you will need the kde-config-gtk package).

You should then be able to set the GTK look and feel in java applications. You can easily test it with this Java Web Start application.