XZ for Java 1.6 is available at <http://tukaani.org/xz/java.html> and in the Maven Central (groupId = org.tukaani, artifactId = xz). Here is an extract from the NEWS file:
* Fix LZMA2Options.getInputStream to work with a preset dictionary. * Make it possible to disable verification of integrity checks in XZ decompression. It should almost never be used but may be useful in some rare situations. This feature is available via new constructors in XZInputStream, SingleXZInputStream, and SeekableXZInputStream. * Add LZMAOutputStream for encoding to raw LZMA (i.e. LZMA1) streams and to the legacy .lzma format. -- Lasse Collin | IRC: Larhzu @ IRCnet & Freenode