How to create core.jar using Terminal in Mac?

How to create core.jar using Terminal in Mac?

I have downloaded zxing-2.2 from the following link:
https://code.google.com/p/zxing/downloads/list
I am navigate to the root directory of the downloaded zxing-2.2 folder and
executing following command to create core.jar :
ant -f core/build.xml
Following is the output i see in terminal:
Buildfile: /Users/Piscean/Desktop/zxing-2.2/build.xml
release:
[zip] Building zip: /Users/Piscean/Desktop/zxing-2.2/ZXing-2.2.zip
[zip] Warning: skipping zip archive
/Users/Piscean/Desktop/zxing-2.2/ZXing-2.2-testdata.zip because no files
were included.
BUILD SUCCESSFUL
Total time: 2 seconds
But it does not create any core.jar in core folder. But it creates a new
ZXing-2.2.zip in zxing-2.2 folder. Am i doing something wrong? How can i
create core.jar ? Thanks in advance.