I saw that but there is no indication of what version of GB18030 is supported and whether or not the JDK is certified for GB18030-2000 or GB18030-2005.
I can only assume, by the release notes of J2SE 1.4 that GB18030-2005 is not supported on that particular version because the unicode support is based on Unicode 3.0 and GB18030-2005 was introduced on/after Unicode 4.1.
I can't find anything for J2SE 1.5 or 1.6 that indicates what version of GB18030 is supported or even what version of Unicode is supported.
This API documentation:
is for Java 5 and it says Unicode 4.0 is supported. This documentation:
is for Java 6 and it says Unicode 4.0 is supported.
Okay, I googled "GB18030 certification" and came up with some articles:
[A Look at Chinas New GB 18030 Character Set Standard|http://www.lisa.org/globalizationinsider/2002/05/a_look_at_china.html]
[GB18030-2000 - The New Chinese National Standard|http://developers.sun.com/dev/gadc/technicalpublications/articles/gb18030.html]
Both are not especially recent but the latter suggests to me that Sun might be certified for the 2005 version, or at least that it is probably doing a reasonably good job of implementing it. If you need a definitive statement to that effect then you ought to contact Sun directly. You could read some more articles returned by those keywords too.
I had already found the same articles you pointed out [and many more :-)].
At any rate being "based on Unicode 4.0" as indicated on the API docs, doesn't clarify whether or not JDK 1.5 or 1.6 are GB18030-2005 certified.
At the bottom of the second article you can find a paragraph that states that JDK 1.4 is GB18030-2000 certified with A+ rating. By the way,the CESI changed this rating system in 2004 to "pass" or "fail".
Thanks for taking the time too look into this. It seems that there is no other option but to contact Sun directly for this.