[ excerpt from developer's web site ]

JZlib is a re-implementation of zlib in pure Java. The first and
final aim for hacking this stuff is to add the packet compression
support to pure Java SSH systems.

- Why JZlib?

Java Platform API provides packages 'java.util.zip.*' for accessing
to zlib, but that support is very limited if you need to use the
essence of zlib. For example, we needed to full access to zlib to
add the packet compression support to pure Java SSH system, but
they are useless for our requirements. The Internet draft SSH
Transport Layer Protocol says in the section '4.2 Compression' as
follows,

WWW: http://www.jcraft.com/jzlib/