Java creating .jar file

I'm learning Java and I have a problem. I created 6 different classes, each has it's own main() 开发者_StackOverflowmethod. 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.

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

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.

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.

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......

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.