echo "digraph G {"> diagram.dot
sed -n -e "s/class [ ]*\([a-zA-Z0-9_]*\)[ ]* extends [ ]*\([a-zA-Z0-9_]*\)[ ]*[{][ ]*/\1 -> \2 ;/p" *.java >> diagram.dot
echo "}" >> diagram.dot

http://www.myoutsourcedbrain.com/2009/04/class-dependency-graphs.html

bash 3-line shell script for visualization of java class dependencies with  graphviz. Please see my blog post for details and leave comments there.

Class Dependency Graphs for Java

class, c

Bash