name java files according to their public class declaration

gistfile1.pl

# The regular expression checks for a public class declared in the file.
# The match, captured using the $1 variable, then is used to rename the file according
# to java conventions, i.e. ClassName.java

perl -ne '/public class ([a-zA-Z0-9]+) / && rename($ARGV,$1.".".java)' *

# I created this gist because manning ships the source code for "Hadoop in Action" in files called 
# "listing-2-2", with no indication what kind of file it is.