How to open a JAR file

How do I open a Java JAR file?

Follow these steps to open a JAR file and extract the contents to the local filesystem:

  1. Change the extension of the JAR file from .jar to .zip
  2. Right-click on the JAR file and select Extract All
  3. View the contents of the open JAR file on the file system

Is a JAR file just a ZIP file?

A Java JAR file is really just a ZIP file.

Java applications can be made up of hundreds, if not thousands of classes, property files and other artifacts. When a Java application is packaged, all of those resources are zipped up into a single, compressed file.

Open a JAR file

To open a JAR file you can use any standard ZIP utility.

Of course, Java being Java, we can’t just call a ZIP file a ZIP file. We must call it something cute.

In Java, we create JavaBeans. And where should JavaBeans be stored? They should be stored in a jar file. Which is why we use the term JAR in Java, and not ZIP.

But the fact is, if you open a Java JAR file, you’re really just opening a ZIP file that contains all of the resources a Java app needs to run.

What does JAR stand for?

JAR is an acronym used to abbreviate the term Java ARchive.

Because JAR is an acronym, we capitalize each letter. We also pronounce the full word ‘jar.’

We do not say each letter individually as you would with an italicization like JDK or JRE.

Java JAR Zip File

A Java JAR file uses a standard compression algorithm used by programs like 7-Zip and Gzip.

Run or open a JAR file?

Sometimes when a person uses the term ‘open a JAR file’ they really mean they want to run a JAR file.

To run a JAR file you must first install Java on your computer.

With Java installed, you can run the JAR file on the command line with the following command:

java -jar jarfilename.jar

This will search for the main-class in the JAR file and run it.

Extract the contents of a JAR

When you install Java, the Java JAR utility also gets installed. This utility can both create JAR files and open JAR files.

To extract the contents of a JAR file to the filesystem with the Java JAR utility, just issue the following command:

jar xf jar-file-name [files-to-open]
Open a JAR Java command
JAR Option Meaning
jar The Java utility to create and open JAR files
x option Indicates the files in the JAR should be extracted
f option Specifies the name of the JAR to open
jar-file-name The name of the JAR to open and extract
files-to-open Optional command to specify which files in the JAR to open and extract

The Java JAR file in review

The JAR file is an important artifact in the world of Agile software development in Java.

But the JAR file is really just a ZIP file with a different file extension. If you ever need to open a JAR file, any ZIP utility that uses a standard compression algorithm is more than sufficient to perform the task.

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