How to Create and Execute a .Jar File in Linux Terminal

A JAR (Java ARchive) is platform-independent file format used to aggregate many Java class files and associated metadata and resources such as text, images, etc, into a single file for distribution.

It allows Java runtimes to efficiently deploy an entire application in one archive file, and provides many benefits such as security, its elements may be compressed, shortening download times, allows for package sealing and versioning, supports portability. It also supports packaging for extensions.

In this article, we will show how to create a simple Java application and bundle it into a JAR file, and demonstrate how to execute a .jar file from the Linux terminal.

To do this, you must have java command line tool installed to launche a Java application, and the -jar flag to execute a program encapsulated in a JAR file. When this flag is used, the specified JAR file is the source of all user classes, and other class path settings are ignored.

How to Create a JAR File in Linux

1. First start by writing a simple Java class with a main method for an application called TecmintApp, for demonstration purpose.

$ vim TecmintApp.java

Copy and paste the following code to TecmintApp.java file.

public class TecmintApp {
	public static void main(String[] args){
		System.out.println(" Just executed TecmintApp! ");
	}
}

Save the file and close it.

2. Next, we need to compile and pack the class into a JAR file using the javac and jar utilities as shown.

$ javac -d . TecmintApp.java
$ ls
$ jar cvf tecmintapp.jar TecmintApp.class
$ ls

3. Once tecmintapp.jar created, now you can excute the file using java command as shown.

$ java -jar tecmintapp.jar

no main manifest attribute, in tecmintapp.jar

From the output of the above command, we encountered an error. The JVM (Java Virtual Machine) couldn’t find our main manifest attribute, thus it could not locate the main class containing the main method (public static void main (String[] args)).

The JAR file should have a manifest that contains a line in the form Main-Class:classname that defines the class with the main method that serves as our application’s starting point.

4. To fix the above error, we will need to update the JAR file to include a manifest attribute together with our code. Let’s create a MANIFEST.MF file.

$ vim MANIFEST.MF

Copy and paste the following line to MANIFEST.MF file.

Main-Class:  TecmintApp

Save the file and let’s add the file MANIFEST.MF to our tecmintapp.jar using following command.

$ jar cvmf MANIFEST.MF tecmintapp.jar TecmintApp.class

5. Finally, when we executed the JAR file again, it should produce the expected result as shown in the output.

$ java -jar tecmintapp.jar

Just executed TecmintApp!

For more information, see the java, javac and jar command man pages.

$ man java
$ man javac
$ man jar

Reference: Packaging Programs in JAR Files.

That’s all! In this short article, we have explained how to create a simple Java application and bundle it into a JAR file, and demonstrated how to execute a .jar file from the terminal. If you have any questions or supplementary ideas to share, use the feedback form below.

Hey TecMint readers,

Exciting news! Every month, our top blog commenters will have the chance to win fantastic rewards, like free Linux eBooks such as RHCE, RHCSA, LFCS, Learn Linux, and Awk, each worth $20!

Learn more about the contest and stand a chance to win by sharing your thoughts below!

Aaron Kili
Aaron Kili is a Linux and F.O.S.S enthusiast, an upcoming Linux SysAdmin, web developer, and currently a content creator for TecMint who loves working with computers and strongly believes in sharing knowledge.

Each tutorial at TecMint is created by a team of experienced Linux system administrators so that it meets our high-quality standards.

Join the TecMint Weekly Newsletter (More Than 156,129 Linux Enthusiasts Have Subscribed)
Was this article helpful? Please add a comment or buy me a coffee to show your appreciation.

1 Comment

Leave a Reply

Got Something to Say? Join the Discussion...

Thank you for taking the time to share your thoughts with us. We appreciate your decision to leave a comment and value your contribution to the discussion. It's important to note that we moderate all comments in accordance with our comment policy to ensure a respectful and constructive conversation.

Rest assured that your email address will remain private and will not be published or shared with anyone. We prioritize the privacy and security of our users.