Java not working? (minecraft related)?

I know how to install forge but every time I try to, a window pops up saying, "Error: Invalid or corrupted jar file." It does this with all my jar files or it doesn't open at all. It only stated doing this today. I don't know why its doing that or how to fix it.

If the problem is with all of your jar files,
then it's most likely the problem in JVM, not Forge.
You should reinstall Java.