for java i heard about OpenCms for developing a good web application. but i want to know that which cms is mostly used for java application . i am beginner for CMS if OpenCms is good one , from where i start to learn this.
All major CMSes have lots of developer documentation on their web site; that should be your starting point. While OpenCms is a powerful product, I advise to check out at least Alfresco and dotCms as well before making a choice.