Creating a Jar file in Java

The JDK's jar (Java Archive) tool offers the ability to produce jar files that can be executed. If you double-click a jar file that is executable, it will call the class' main() method.

You must produce an a.mf file, also known as a manifest file, in order to create an executable jar file.

A manifest file is created

We must type Main-Class, a colon, a space, and the class name, then enter to create a manifest file. For instance:

myfile.mf

Main-Class: Abc

The mf file begins with the Main-Class colon gap class name, as you can see. Here, CJFE is the class name.

Just after the class name in the mf file, a new line is required.

using the jar tool to create an executable jar file

The jar tool offers a variety of switches, some of which are listed below:

1. -c generates a fresh archive file.
2. The output that is verbose is produced using the -v option. The extracted or included resource is shown on the standard output.
3. The -m option includes manifest data from the specified mf file.
4. -f specifies the name of the archive file.
5. The -x option extracts files from the archive file.

Let's now write the code necessary to create an executable jar from a mf file.

You must type jar, switches, mf file, jar file, and then as shown in the .classfile:

jar -cvf MyJarFile.jar Abc.class

for running or executing the class file which is in the far file we should use this command.

java -cp MyJarFile.jar Abc

We are presuming that you have used AWT or SWING to develop any window-based applications. If not, you can just use the following code:

Abc.java

import javax.swing.*;    
public class Abc{    
Abc(){    
JFrame f=new JFrame();    
                    
JButton b=new JButton("Click Here");    
b.setBounds(130,100,100, 40);    
        
f.add(b);    
            
f.setSize(300,400);    
f.setLayout(null);    
f.setVisible(true);    
            
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);    
}    
public static void main(String[] args) {    
    new Abc();    
}    
}

Output:

This is what the jar file looks like:

If we double, click on the myjar file then it will display as shown below.