Java creating .jar file

Question

I'm learning Java and I have a problem. I created 6 different classes, each has it's own main() method. I want to create executable .jar for each class, that is 6 executable .jar files.

So far I tried

java -jar cf myJar.jar myClass.class 

and I get 'Unable to access jarfile cf'. I'm doing something wrong but I don't know what. I'm also using Eclipse IDE if that means something.

Answer 1

In order to create a .jar file, you need to use jar instead of java:

jar cf myJar.jar myClass.class 

Additionally, if you want to make it executable, you need to indicate an entry point (i.e., a class with public static void main(String[] args)) for your application. This is usually accomplished by creating a manifest file that contains the Main-Class header (e.g., Main-Class: myClass).

However, as Mark Peters pointed out, with JDK 6, you can use the e option to define the entry point:

jar cfe myJar.jar myClass myClass.class  

Finally, you can execute it:

java -jar myJar.jar 

See also

• Creating a JAR File
• Setting an Application's Entry Point with the JAR Tool

Answer 2

Sine you've mentioned you're using Eclipse... Eclipse can create the JARs for you, so long as you've run each class that has a main once. Right-click the project and click Export, then select "Runnable JAR file" under the Java folder. Select the class name in the launch configuration, choose a place to save the jar, and make a decision how to handle libraries if necessary. Click finish, wipe hands on pants.