Exceptions concepts

• exceptions are used to model errors
• should only catch an exception if in a place to deal with it
• exceptions trickle down the execution nest stack until they are caught OR reach the end and crash the program

  
• squelching exceptions - having an empty catch in a try catch to silence an exception. tempting to do this for checked exceptions to silence the compiler
• good ones to know are illegalStateException and IllegalArgumentException
• can create custom exceptions as subclasses of the next best fitting one