— Scott McNealy, Sun Microsystems Chairman, President and ceo

592
 
chapter 17
When your class is in a package, the package directory structure 
must be inside the JAR! You can’t just pop your classes in the 
JAR the way we did pre-packages. And you must be sure that you 
don’t include any other directories above your package. The 
fi rst directory of your package (usually com) must be the fi rst 
directory within the JAR! If you were to accidentally include the 
directory above the package (e.g. the “classes” directory), the JAR 
wouldn’t work correctly.
PackageExercise.class
classes
com
headfirstjava
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Making an executable JAR with packages
JAR
Making an executable JAR
1
Make sure all of your class fi les are 
within the correct package structure, 
under the classes directory.
2
Create a manifest.txt fi le that states 
which class has the main() method, 
and be sure to use the fully-qualifi ed 
class name!
Make a text fi le named manifest.txt that has a
single line:
Main-Class: com.headfi rstjava.PackageExercise
Put the manifest fi le into the classes directory
3
Run the jar tool to create a JAR fi le 
that contains the package directories 
plus the manifest
%cd MyProject/classes 
%jar -cvmf manifest.txt packEx.jar com
packEx.jar
classes
manifest.txt
classes
com
headfirstjava
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Main-Class: MiniApp
PackageExercise.class