What is the best way to encrypt form data from client end javascript and decrypt at server side Java?
If you are not using SSL/TLS on the web server, any man-in-the-middle can tamper with the javascript code as it is pushed from the server to the client. At that point, an attacker can disable any client-side protections you have added. So, without SSL/TLS, anything you do is basically useless.

Now, once you enable SSL/TLS on the server and force users to connect via that secure connection, all information is protected in transit already, so no additional protections are needed.

So, enable SSL/TLS on the server and force all connections to use that and you are good to go.