Selenium TestNG - Running Multiple TestNG Classes using Java Main Class

List file=new ArrayList();
file.add("/home/selenium-workspace/starauto/starEE.xml");
file.add("/home/selenium-workspace/starauto/starDD.xml");
TestNG testSTAR = new TestNG();
testSTAR.setTestSuites(file);
testSTAR.run();

Seleinum installation in BOSS Linux

Step:1

sudo apt-get install python-pip

Step:2 

pip install -U selenium

for python3 and more install  

Step:1 sudo apt-get install python-pip3

Step:2  python3.7 -m pip install -U selenium