JMaterial-UI is a swing UI library that implements Google's material design guidelines. The current is still in development and is not currently intended for use. Some things suggested in the guidelines aren't possible in swing and will be changed to best fit the limitations. I am currently working on the buttons and hope to have a distribution ready later on this year. Alongside all that I will also be creating some demonstration programs and a documentation.
If you are in anyway interested in helping out you can get in contact with me via my email: trentnoskcaj@gmail.com.
To see progress as of current take a look at the JMaterial-UI trello board