File Extension JAR

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JAR File Extension Description

The file extension JAR is used generally used to allocate classes of Java and associated metadata.

JAR Files were developed by Sun Microsystems to provide users with the file format for data compression and file archive. One of the basic functions of files with the .JAR file extension is to aggregate several files into a single file.

Steps to fix and open .JAR Files

If .JAR files wont open on your computer then follow these steps:

1. Make sure you have one of the programs above installed. If you do and .JAR files still wont open then proceed to step two below.
2. Ensure Windows is set to open .JAR files with the appropriate program. The easiest way to do this is to download Filecure and then select the manage tab on the left. This feature is available free in the Filecure application.
3. If the problem persists then download Filecure if you haven't already, and Click the big green "Start Scan" Button. It takes about 30 seconds to scan your computer for all file extension associations. Once the scan is finished you will see if any problems are detected. If so then Click the Green "Fix Now" Button.
4. Try to open your .JAR File again, The problem should be fixed.

If you still have issues with this file, please click the Ask a Question button at the top right corner of this page.

Create and Extract JAR Files

One method of creating and extracting files with the .JAR file extension is to use the ?JAR? command that automatically comes with the Java Development Kit, which is a tool also developed by Sun Microsystems for Java developers. In addition, the methods can also be done through the use of several zip tools available today.

Within a single file with the .JAR file extension is an optional manifest file situated in the META-INF/ MANIFEST.MF path. Manifest files are specific files that are normally contained within an archive for JAR. More so, these kinds of files are utilized to define the package and extension related data.

How Manifest Files work with JAR Files

Through the use of manifest files, the purposes of the files with the .JAR file extension can be determined. For instance, files with the .JAR file extensions will have one of their classes categorized as the main class if they are intended to be standalone programs. Using this example, the manifest file would have an entry, such as: ?Main-Class: myPrograms.MyClass?.

The file extension JAR can also have an entry called Classpath, which can identify other files with the .JAR file extension to be loaded with the Java Archive. Additionally, the entry can also consist of a roster of relative or absolute paths to other files with the .JAR file extension.

Files with the .JAR file extension can also be digitally signed though the user or developer must add the significant signature information into the manifest file. The moment when the Java runtime loads files with the .JAR file extensions that are signed, it can authenticate the signatures within them and disallow classes that do not match the signature to load.

• Properties:

• Common Path:
  META-INF/ MANIFEST.MF, Classpath
• Associated Applications:
  Java Runtime 1.1, Web browsers with Java support

Additional JAR File Info:

Sun Microsystems , JAR File Created by: http://www.sun.com/

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