I posted a few weeks ago with regards to downloading the JAVA API as a PDF file. However, it does seem as though Oracle is reluctant to allow this. Seemingly it prefers that JAVA users access the documentation online!
Of course, if a company does not wish to release their documentation in a PDF download, that is their prerogative.
In this post, I wish to offer an alternative and rather simple method of getting the API information you require (admittedly still not in PDF) downloaded to your device so you have access to the information you need at any time!
First, download and install the freeware at the link below! It's entirely free! Not even any ads!
On the above java web page select the correct link for the flavour of JAVA you are interested in until you get to the specific documentation you wish to download. Once you find the page with the documentation you want, copy and paste the web address into HTTRACK set it to download 4 or 5 links deep!
You can have the entire API documentation downloaded to your PC. Ok, it's still in html format, but it will still work even if your offline, obviously!