Java Gui better in Windows?

    So why does java gui look better in Windows than in Linux? In particular, in one of my programs, JFrames and JDialogs are already too spacious in Windows while still really short in linux (see pictures below). Is it the case that the Linux version of the appletviewer, the java interpreter etc. included in the Java Development Kit (jdk) for Linux, are all outdated and needs upgrade? If the jdk in Windows is better than that in linux, then can we say that Sun is focusing more on their Windows product? Maybe that is because there are still far more Windows users but I am pretty sure that Linux would catch up specially in a developing country like my country, the Philippines. The current state of tools I am using in windows and in linux somehow would make me write a two ports- a Linux version and a Windows version. What happens now to Java's write once, run for all supposed feature?

Environment:
Windows 98SE, j2sdk-1_4_1_02-windows-i586
and
Mandrake 9.2, Mozilla 1.4, Galeon 1.3.8, j2sdk-1_4_2_02-linux-i586-rpm.bin

    You may also see this yourself if you have jdk on both Linux and Windows. The software tested is here.

Looks really slick in Windows. Notice where "Java Applet Window" is written in the dialog.


This is the Linux version. The "Java Applet Window" is written on top of the dialog as opposed to below in Windows. Notice also that the buttons are concealed.


This is the frame version of the previous program in Windows.


Spot the difference!

Note:
    This seems to be already fixed in version 1_4_2_06 of the SDK. But still, it remains that there are differences (albeit maybe really subtle) between the JDK released for Windows and that released for Linux or any other OS.