1. To prevent junkware prompts during the initial install, download the installer from oracle instead of java.com, because the oracle installer does not have the junkware prompt:
(searching for "java oracle download" will get you there)
2. To prevent junkware prompts during the updates, disable Java Sponsors.
A java.com FAQ claims that in 7u65 or later, you can find a "Suppress sponsor offers when updating Java" option in the Java Control Panel's Advanced tab, but I have never seen it there, possibly because I have issued the regkey fix. To do that, save the following text to a file titled "disable-java-sponsers.reg" and double-click the file:
Windows Registry Editor Version 5.00
The answer of "Don't install Java at all, problem solved" is great and I wholeheartedly recommend it for those who don't need to run it, but there are many who have no choice and must run it for work, banking, Minecraft, etc. Using the regkey fix is great to prevent clueless family (grandparents!) and friends who need to run Java from accidentally installing the junkware.