Can I build website completely using Java?

Answer 1

Look into Java Spring MVC and JSP. You will still need top know HTML and CSS at the least for front end. Maybe some javascript too, depending on what you're doing.

Answer 2

If you meant using only Java on the server side, Yes. Why not?

Answer 3

Yes if you're meaning to build dynamically web documents...

... but no if you're meaning to avoid Html/Css stuff ^^