Java I/O

Data Compression

Java supports several related compression formats, including zlib, deflate, and gzip. These formats are documented in RFCs 1950, 1951, and 1952, and are available wherever RFCs are found, including http://www.faqs.org/rfcs/. The master site for these particular RFCs is ftp://ftp.uu.net/graphics/png/documents/zlib/zdoc-index.html.

Java’s compression classes are native wrappers around the ZLIB compression library written by Jean-Loup Gailly and Mark Adler. You can learn about this library at http://www.cdrom.com/pub/infozip/zlib/.

For more general information about compression and archiving algorithms and formats, the http://comp.compression FAQ is a good place to start. See http://www.faqs.org/faqs/compression-faq/part1/preamble.html. More technical details and sample code in C for a variety of algorithms are available in The Data Compression Book, by Mark Nelson and Jean-Loup Gailly (M&T Books, 1996, ISBN 1-55851-434-1).

The JAR file format was developed by Sun for Java. The full specification can be found at http://java.sun.com/products/jdk/1.2/docs/guide/jar/jarGuide.html ( Java 2) or http://java.sun.com/products/jdk/1.1/docs/guide/jar/jarGuide.html ( Java 1.1). Aside from the name, the only thing that really distinguishes a JAR file from a zip file is the optional manifest of the contents. The manifest format specification can be found at http://java.sun.com/products/jdk/1.2/docs/guide/jar/manifest.html.