I dont get exceptions

Most every programming language has exceptions, but I dont understand the need for them over regular error checking code. I took a Java course and we just used regular if statements to check input values from IO and it worked perfectly fine. Ive heard exceptions are not allowed in highly critical code as it makes unpredictable runtime logic. Can someone tell me what exceptions offer beyond error checking code that you could write on your own?

>>3
Oh fuck, I feel stupid. I was myself thinking that a proper exception system would allow for actually handling exceptional conditions and continuing execution, rather than just "reporting" an exception to the nearest handler and aborting. Now thanks to your post I realized that you really only need a call/cc.
In my defense, I haven't really programmed in a Lisp yet.