Thread:User talk:Nischayn22/CopyToClipboardAndThenPasteFromClipboardToFacebookCommentBox?/reply

This isn't so easy to do, see http://stackoverflow.com/questions/4244822/copy-paste-content-to-and-from-clipboard-using-javascript for a discussion on the needed feature. I assume you meant Javascript and not Java, but the Javascript solution only works with IE.