This is a little known feature borrowed from zlib, and possibly predates even that.
I ran into this many moons ago while working on a large J2ME app, trying to shrink the zip file. We hit the point where looking a lot the compression algorithm was our next most reasonable step, and since I had prior zlib experience decoding PNGs, I dug into it.
I discovered that Sun had partly exposed the dictionary support and I ended up filing an enhancement request and some numbers for my POC. But as it turns out Sun had already begun work on their dense archive format which achieved a multiple of the improvements I was getting, so it went nowhere.
Alphabetizing the constant pool got us a fraction of the benefit, and I discovered that because of the way the constants are stored, suffix sorting them got us another 1.1% compression so I dropped it.
I ran into this many moons ago while working on a large J2ME app, trying to shrink the zip file. We hit the point where looking a lot the compression algorithm was our next most reasonable step, and since I had prior zlib experience decoding PNGs, I dug into it.
I discovered that Sun had partly exposed the dictionary support and I ended up filing an enhancement request and some numbers for my POC. But as it turns out Sun had already begun work on their dense archive format which achieved a multiple of the improvements I was getting, so it went nowhere.
Alphabetizing the constant pool got us a fraction of the benefit, and I discovered that because of the way the constants are stored, suffix sorting them got us another 1.1% compression so I dropped it.