Will my Java based website be available for thousands of users while, I am coding like if there is only one user accessing the resources at a time?

After learning advance Java, I am creating my first website in Java using Tomcat server. But it seems like I am creating my website in such a way that there is only one user accessing the resources. Will my website work, when thousands of users would be accessing my website? Will it be handled by Tomcat anyhow or do I have to write code thousands of times so that thousands of users can access it at the same time?