open your terminal and install java-1.7 jre
# cd in the game directory
$ cd ~/JavaTetris
# setting CLASSPATH
$ export CLASSPATH=./bin:./lib/dom4j-1.6.1.jar:./lib/mysql-connector.jar
#run and enjoy
$java main.Main
open your terminal and make sure using javac which version is 1.7
# cd in the game directory and make a bin dir
$ cd ~/JavaTetris;mkdir bin
# compile everything to the bin directory
$ javac -d bin -cp lib/dom4j-1.6.1.jar:lib/mysql-connector.jar src/*/*.java src/*/*/*.java