Java Archive.

A file format developed by Sun to store compressed Java programs. All the program's needed .class and support files can be stored in a single .jar file.

Tool for creating archive files, shipped with JDK.

Usage syntax:

jar c|t|x[f][m][v] [jarfile] [manifestfile] files...


First letter is for create/list/extract, just like in tar program. from is used to say you want to read/write from/to a file jarfile (if not specified, it will read/write from/to standard input/output. m option is used with creation option to add stuff in manifestfile to the archive's MANIFEST. v just increases verbosity. All in all, very much like tar's syntax.

There are other options too, but they're less needed. Just type "jar" to get a summary.

jar cvf myproggie.jar *.class
jar cvmf myproggie.jar moneyfest.stub *.class

The JAR archives are normal zip archive files, but they typically contain a file called META-INF/MANIFEST that lists the files and other wacky parameters.

Handy Tip: In Java2 (JDK 1.2 and later), it's possible to add a parameter "Main-Class" to the manifest file to tell which class has the main() method. Like this:

$ echo "Main-Class: Frobnicator" > mainclass.stub
$ jar cvfm frobnicator.jar mainclass.stub *.class

This makes distributing and using the program much easier because you can say stuff like this to start the program:

$ java -jar frobnicator.jar

Remember ARJ? Yeah, warez d00ds first choice back in the good 'ol days before RAR grew strong.
The same company which created and still maintains ARJ, about the time when ARJ was falling from grace, created JAR which still seems to be a sort of ugly duckling.

JAR is a MS-DOS and WIN32 compatible, command line operated file archiver program. As of my knowledge, there is no GUI available for it. It's got almost all features ARJ has, which includes:

  • long (FAT32, NTFS) filename support
  • automated splitting (aka spanning) of the archive in aribitary lengths
  • ANSI-style comments
However, it wouldn't be another (newer) program, if it wouldn't have an edge above ARJ:
  • decent compression rates (similar to RAR or TAR/GZIP, small files are concatenated before compression, thus increasing compression rates)
  • multiple backups of the same files, using incremental compression
  • file version management

Compression rates of JAR usually even exceed RAR (a bit) while being significantly faster, however those are old numbers (RAR version 2.00 beta 3) and may have changed now. JAR compresses much better than PKZIP (ver. 2.04g), differences ranging from 15% up to 40%. On the downside, JAR is significantly slower than ZIP, especially with when used on a large number of files.

From my personal experience, I love JAR's ability to create multiple, versioned backups of the same file (-tree). Running once per day as a scheduled task, it is possible to fully restore any archived snapshot.

You can get an (almost) fully working shareware version from The shareware version only lacks the JAR security envelope, which resembles some sort of combined encryption and signation, but who needs that in days of PGP/GNUPG?

most information, especially compression rate comparisons, diabolically ripped from

Jar (?), n. [See Ajar.]

A turn. [Only in phrase.]

On the jar, on the turn, ajar, as a door.


© Webster 1913.

Jar (?), n. [F. jarre, Sp. jarra, from Ar. jarrah ewer; cf. Pers. jarrah.]


A deep, broad-mouthed vessel of earthenware or glass, for holding fruit, preserves, etc., or for ornamental purposes; as, a jar of honey; a rose jar.



The measure of what is contained in a jar; as, a jar of oil; a jar of preserves.

Bell jar, Leyden jar. See in the Vocabulary.


© Webster 1913.

Jar, v. i. [imp. & p. p. Jarred (?); p. pr. & vb. n. jarring (?).] [Cf. OE. charken to creak, AS. cearcian to gnash, F. jars a gander, L. garrire to chatter, prate, OHG. kerran to chatter, croak, G. quarren to grumble, and E. jargon, ajar.]


To give forth a rudely quivering or tremulous sound; to sound harshly or discordantly; as, the notes jarred on my ears.

When such strings jar, what hope of harmony ? Shak.

A string may jar in the best master's hand. Roscommon.


To act in opposition or disagreement; to clash; to interfere; to quarrel; to dispute.

When those renowned noble peers Greece Through stubborn pride among themselves did jar. Spenser.

For orders and degrees Jar not with liberty, but well consist. Milton.


© Webster 1913.

Jar, v. t.


To cause a short, tremulous motion of, to cause to tremble, as by a sudden shock or blow; to shake; to shock; as, to jar the earth; to jar one's faith.


To tick; to beat; to mark or tell off.


My thoughts are minutes, and with sighs they jar Their watches on unto mine eyes. Shak.


© Webster 1913.

Jar, n.


A rattling, tremulous vibration or shock; a shake; a harsh sound; a discord; as, the jar of a train; the jar of harsh sounds.


Clash of interest or opinions; collision; discord; debate; slight disagreement.

And yet his peace is but continual jar. Spenser.

Cease, cease these jars, and rest your minds in peace. Shak.


A regular vibration, as of a pendulum.

I love thee not a jar of the clock. Shak.

4. pl.

In deep well boring, a device resembling two long chain links, for connecting a percussion drill to the rod or rope which works it, so that the drill is driven down by impact and is jerked loose when jammed.


© Webster 1913.

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