— Scott McNealy, Sun Microsystems Chairman, President and ceo

com
headfirstjava
101101 
10 110 1 
0 11 0 
001 10 
001 01 
PackageExercise.class
All you specify is the 
com directory! And 
you’ll 
get everything in it!
The only thing you need to include is the ‘com’ 
directory, and the entire package (and all classes) 
will go into the JAR.
JARs and 
packages

---

package, jars 
and
deployment
you are here
4
593
So where did the manifest file go?
-tf stands for ‘Table File’ as in 
“show me a table of the JAR file”
we put the JAR file into a 
directory named Skyler
Why don’t we look inside the JAR and fi nd out? From the 
command-line, the jar tool can do more than just create and run a 
JAR. You can extract the contents of a JAR (just like ‘unzipping’ or 
‘untarring’).
Imagine you’ve put the packEx.jar into a directory named Skyler. 
packEx.jar
jar commands for listing and extracting 
1
List the contents of a JAR
% jar -tf packEx.jar
File Edit Window Help Pickle
% cd Skyler
% jar -tf packEx.jar
META-INF/
META-INF/MANIFEST.MF
com/
com/headfirstjava/
com/headfirstjava/
PackageExercise.class
-xf stands for ‘Extract File’ and it 
works just like unzipping or untarring. 
If you extract the packEx.jar, you’ll 
see the META-INF directory and the 
com directory directory in your current 
directory 
2
Extract the contents of a JAR (i.e. unjar)
% cd Skyler
% jar -xf packEx.jar
MANIFEST.MF
Main-Class: MiniApp