Apache Derby is the cauldron where Sun and other Apache participants forge what later becomes "Java DB" a database shipped with every copy of the JDK!

It was amazing that unlike years past, the only commands I needed to execute on this laptop to get source and do a build where these:

svn co https://svn.apache.org/repos/asf/db/derby/code/trunk derby2009
ant -quiet buildsource

All other software, including ant and svn as well as all the libraries, already existed on this laptop.

...
BUILD SUCCESSFUL
Total time: 43 seconds

The jars took 14 seconds to put together!

ant -quiet buildjars
BUILD SUCCESSFUL
Total time: 14 seconds

The build instructions modestly point out that we need to wait a bit longer for the Javadocs:

ant -quiet javadoc
BUILD SUCCESSFUL
Total time: 1 minute 46 seconds

A simple verification

java -jar jars/sane/derbyrun.jar sysinfo

reminds the user politely what has been built:

...
10.6.0.0 alpha - (772044)

You can also build the development tests and test Derby.

A "derbyall" test took my machine about 44 minutes to execute:

Summary results:

Test Run Started: 2009-05-06 12:54:43.0
Test Run Duration: 00:44:47

663 Tests Run
96% Pass (640 tests passed)
 4% Fail (23 tests failed)
15 Suites skipped

Of course, this is for an alpha branch.

Ultimately, to build Derby, you should use the definitive guidelines.