Java JAR File Compression
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File Compression
“Items stored in JAR files are compressed with the standard ZIP file compression. Compression makes downloading classes over a network much faster. A quick survey of the standard Java distribution shows that a typical class file shrinks by about 40% when it is compressed. Text files such as HTML or ASCII containing English words often compress to one-tenth their original size or less. (On the other hand, image files don’t normally get smaller when compressed, as most common image formats are themselves a compression format.)” (B086L2NYWR)
“Java also has an archive format called Pack200, which is optimized specifically for Java class bytecode and can achieve over four times’ greater compression of Java classes than ZIP alone.” (B086L2NYWR)