Well, the only solutions (that may or may not work) that I see is
1. Scan your PC. Somethings messing up Java/Minecraft as someone already said...
What antivirus do you use? (I recommend Bitdefender)
2. Not exactly a solution but maybe something wrong with your connection to Mojang's servers? Dunno, just a pretty big "maybe".
3. Delete EVERY minecraft related files on your PC. And Java for that case. When done, install Java 8 and JDK 8 (64 bit if you have 64 bit CPU)
Not recommended but if none of those works, reinstall your PC =/