You can use the
jar command to create an archive for classes and resources, and to manipulate or restore individual classes or resources from an archive.
jar [OPTION...] [ [--release VERSION] [-C dir] files] ...
jar command is a general-purpose archiving and compression tool, based on the ZIP and ZLIB compression formats. Initially, the
jar command was designed to package Java applets (not supported since JDK 11) or applications; however, beginning with JDK 9, users can use the
jar command to create modular JARs. For transportation and deployment, it’s usually more convenient to package modules as modular JARs.
The syntax for the
jar command resembles the syntax for the
tar command. It has several main operation modes, defined by one of the mandatory operation arguments. Other arguments are either options that modify the behavior of the operation or are required to perform the operation.
When modules or the components of an application (files, images and sounds) are combined into a single archive, they can be downloaded by a Java agent (such as a browser) in a single HTTP transaction, rather than requiring a new connection for each piece. This dramatically improves download times. The
jar command also compresses files, which further improves download time. The
jar command also enables individual entries in a file to be signed so that their origin can be authenticated. A JAR file can be used as a class path entry, whether or not it’s compressed.
An archive becomes a modular JAR when you include a module descriptor,
module-info.class, in the root of the given directories or in the root of the JAR archive. The following operations described in Operation Modifiers Valid Only in Create and Update Modes are valid only when creating or updating a modular JAR or updating an existing non-modular JAR:
All mandatory or optional arguments for long options are also mandatory or optional for any corresponding short options.
Main Operation Modes
When using the
jar command, you must specify the operation for it to perform. You specify the operation mode for the
jar command by including the appropriate operation arguments described in this section. You can mix an operation argument with other one-letter options. Generally the operation argument is the first argument specified on the command line.
Creates the archive.
Generates index information for the specified JAR file.
Lists the table of contents for the archive.
Updates an existing JAR file.
Extracts the named (or all) files from the archive.
Prints the module descriptor or automatic module name.
Operation Modifiers Valid in Any Mode
You can use the following options to customize the actions of any operation mode included in the
Changes the specified directory and includes the
filesspecified at the end of the command line.
jar [OPTION...] [ [--release VERSION] [-C dir] files]
Specifies the archive file name.
Creates a multirelease JAR file. Places all files specified after the option into a versioned directory of the JAR file named
META-INF/versions/VERSION/, where VERSION must be must be a positive integer whose value is 9 or greater.
At run time, where more than one version of a class exists in the JAR, the JDK will use the first one it finds, searching initially in the directory tree whose
VERSIONnumber matches the JDK's major version number. It will then look in directories with successively lower
VERSIONnumbers, and finally look in the root of the JAR.
Sends or prints verbose output to standard output.
Operation Modifiers Valid Only in Create and Update Modes
You can use the following options to customize the actions of the create and the update main operation modes:
Specifies the application entry point for standalone applications bundled into a modular or executable modular JAR file.
Includes the manifest information from the given manifest file.
Doesn’t create a manifest file for the entries.
Specifies the module version, when creating or updating a modular JAR file, or updating a non-modular JAR file.
Computes and records the hashes of modules matched by the given pattern and that depend upon directly or indirectly on a modular JAR file being created or a non-modular JAR file being updated.
Specifies the location of module dependence for generating the hash.
jaroptions and file names from a text file.
An options file is a text file that contains the options and values that you would typically enter in a command prompt. Options may appear on one line or on several lines. You may not specify environment variables for path names. You may comment out lines by prefixing a hash symbol (#) to the beginning of the line.
Operation Modifiers Valid Only in Create, Update, and Generate-index Modes
You can use the following options to customize the actions of the create (
--create) the update (
--update ) and the generate-index (
--generate-index=FILE ) main operation modes:
The following options are recognized by the
jar command and not used with operation modes:
Examples of jar Command Syntax
Create an archive,
classes.jar, that contains two class files,
jar --create --file classes.jar Foo.class Bar.class
Create an archive,
classes.jar, by using an existing manifest,
mymanifest, that contains all of the files in the directory
jar --create --file classes.jar --manifest mymanifest -C foo/
Create a modular JAR archive,
foo.jar, where the module descriptor is located in
jar --create --file foo.jar --main-class com.foo.Main --module-version 1.0 -C foo/classes resources
Update an existing non-modular JAR,
foo.jar, to a modular JAR file.
jar --update --file foo.jar --main-class com.foo.Main --module-version 1.0 -C foo/module-info.class
Create a versioned or multi-release JAR,
foo.jar, that places the files in the
classesdirectory at the root of the JAR, and the files in the
classes—10directory in the
META-INF/versions/10directory of the JAR.
In this example, the
classes/com/foodirectory contains two classes,
com.foo.Hello(the entry point class) and
com.foo.NameProvider, both compiled for JDK 8. The
classes-10/com/foodirectory contains a different version of the
com.foo.NameProviderclass, this one containing JDK 10 specific code and compiled for JDK 10.
Given this setup, create a multirelease JAR file
foo.jarby running the following command from the directory containing the directories
jar --create --file foo.jar --main-class com.foo.Hello -C classes . --release 10 -C classes-10 .
The JAR file
% jar -tf foo.jar META-INF/ META-INF/MANIFEST.MF com/ com/foo/ com/foo/Hello.class com/foo/NameProvider.class META-INF/versions/10/com/ META-INF/versions/10/com/foo/ META-INF/versions/10/com/foo/NameProvider.class
As well as other information, the file
META-INF/MANIFEST.MF, will contain the following lines to indicate that this is a multirelease JAR file with an entry point of
... Main-Class: com.foo.Hello Multi-Release: true
Assuming that the
com.foo.Helloclass calls a method on the
com.foo.NameProviderclass, running the program using JDK 10 will ensure that the
com.foo.NameProviderclass is the one in
META-INF/versions/10/com/foo/. Running the program using JDK 8 will ensure that the
com.foo.NameProviderclass is the one at the root of the JAR, in
Create an archive,
my.jar, by reading options and lists of class files from the file
To shorten or simplify the
jarcommand, you can specify arguments in a separate text file and pass it to the
jarcommand with the at sign (
@) as a prefix.
jar --create --file my.jar @classes.list