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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.

7ochem
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user433947
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6 Answers6

135

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

VH-NZZ
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João Silva
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    This is missing the point isn't it? Are `cf` even valid options to `java`? Either way, he wants to create the jar, not run it. According to the question anyway. – Mark Peters Jan 04 '11 at 20:11
  • @Mark Peters: Typo, I meant jar. Thanks. – João Silva Jan 04 '11 at 20:13
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    In which case you don't need the `-jar` argument do you? Plus, this won't make it executable since you don't specify a manifest. (Apparently in JDK 6+ you can use "e" as a shortcut to avoid supplying the manifest manually: `jar cfe myJar.jar myClass myClass.class`) – Mark Peters Jan 04 '11 at 20:13
  • I always get "no main manifest attribute, in myJar.jar" when I try to run it :/ – Maslor Jul 30 '15 at 16:58
  • If you want executable jar, you'd need to add the manifest file, something like `jar -cvfm out.jar META-INF/MANIFEST.MF src/*.class` – Hritik Jun 20 '20 at 14:42
  • What does `cf` mean here? – Kayvan Shah Apr 18 '23 at 20:47
18

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.

Sean
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10

Often you need to put more into the manifest than what you get with the -e switch, and in that case, the syntax is:

jar -cvfm myJar.jar myManifest.txt myApp.class

Which reads: "create verbose jarFilename manifestFilename", followed by the files you want to include.

Note that the name of the manifest file you supply can be anything, as jar will automatically rename it and put it into the right place within the jar file.

Evgeni Sergeev
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6

way 1 :

Let we have java file test.java which contains main class testa now first we compile our java file simply as javac test.java we create file manifest.txt in same directory and we write Main-Class: mainclassname . e.g : 

  Main-Class: testa

then we create jar file by this command : 

  jar cvfm anyname.jar manifest.txt testa.class

then we run jar file by this command : java -jar anyname.jar

way 2 :

Let we have one package named one and every class are inside it. then we create jar file by this command : 

  jar cf anyname.jar one

then we open manifest.txt inside directory META-INF in anyname.jar file and write 

  Main-Class: one.mainclassname

in third line., then we run jar file by this command : 

  java -jar anyname.jar

to make jar file having more than one class file : jar cf anyname.jar one.class two.class three.class......

Jay Shah
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1

Put all the 6 classes to 6 different projects. Then create jar files of all the 6 projects. In this manner you will get 6 executable jar files.

Arpan Biswas
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0

If you don't want to manually deal with the Manifest file you can use the "e" option. This explicitly defines the entry point in your application.

jar vcfe anyname.jar EntryPoint EntryPoint.class <files to include>

In my case it looked like this

jar vcfe people.jar Peer Peer.class ClientThread.class transport/*

As a result, I was able to run my program with

java -jar people.jar
Hackerman
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