Deflater and Inflater are hard to use correctly, resulting in wrapping code in external libraries and frequent misuse/bugs.

What is needed in most cases is a simple pair of static compress/uncompress methods.

byte[] Deflater.deflate(byte[] uncompressedData)
byte[] Inflater.inflate(byte[] compressedData)

I believe it would be worthwhile adding one override:

byte[] Deflater.deflate(byte[] uncompressedData, int compressionLevel)

Providing these methods would probably deal with 80%+ of end user usages of these classes.