Every time I click the Launcher button I get a message that says "A Java Exception Has Occured" and it will not let me open up the game.

Every time I click the launcer button, the computer says either "A Java Exception Has Occurred" or it says "Downloading Native Launcher", but then says unable to download. I am very concerned because it will not let me play at all and it has never done this before. I have had this account since 2012 and this is the first time I'm having issues with it. Someone please help!