Why is Java NOT used for web front end rather than PHP, Python, Ruby etc. in sites like Facebook, Twitter?

I am not good at JAVA. JAVA is most expensive solution to implement for such websites like facebook or twitter rather than PHP, Python or Ruby.

Development in PHP is100% cheaper than Java for such website. Choosing a language for a project is very important decision in terms for development difficulty, scope and cost including man efforts or other expenses.

Java EE use for website development or making frontend of the website heavy trafic sites or secure web site are made in java EE after take over java by oracle ,oracle remove the2 from  J2EE its very powerful and secure language.