How to creating a JAR? – it’s easy.

Posted on: October 1, 2024 in Java ,

Creating a JAR file in Java involves compiling your Java source code and then packaging the compiled .class files, along with any resources, into a single archive. Here’s a step-by-step guide on how to do it.

1. Compile Your Java Code

Before creating a JAR file, you need to compile your Java source code. This generates the .class files that will go into the JAR.

Command to Compile Java Files:

complile…

javac MyProgram.java

This will create MyProgram.class.

2. Create a Manifest File (Optional but recommended for Executable JARs)

The manifest file (MANIFEST.MF) is an optional file that can specify various metadata about the JAR, such as the entry point (the class with the main() method). If you’re creating an executable JAR, you must specify the Main-Class in the manifest.

Example manifest.txt:

making file

Manifest-Version: 1.0
Main-Class: com.example.Main

Where com.example.Main is the fully qualified name of the class containing your main method.

3. Create the JAR File

Now, use the jar command to create the JAR file. The basic syntax is:

Command to Create a JAR:

command

jar cfm MyApp.jar manifest.txt *.class

c – create a new JAR file.
f – specify the output file name (MyApp.jar).
m – include the manifest file (manifest.txt).
*.class – includes all compiled .class files.

If you’re creating a library JAR (non-executable), you can omit the manifest.txt:

command

jar cf MyLibrary.jar *.class

4. Add Other Files (Optional)

You can also include other resources like images, configuration files, or libraries when creating the JAR. For example:

command

jar cfm MyApp.jar manifest.txt *.class resources/*.png config.properties

5. Running the JAR (For Executable JARs)

Once the JAR file is created, you can run it (if it’s executable) using the java -jar command:

command

java -jar MyApp.jar

Example:

1. Java source file (HelloWorld.java):

java

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    }
}

2. Compile the Java file:

command

javac HelloWorld.java

3. Create a manifest.txt file:

making file…

Manifest-Version: 1.0
Main-Class: HelloWorld

Create the JAR file:

creating…

jar cfm HelloWorld.jar manifest.txt HelloWorld.class

Run the JAR file:

running…

java -jar HelloWorld.jar

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