Exception Handling

Detection and Handling

• The class implementer knows when an error occurs because he wrote the code. He can detect bad parameters, NULL pointers, etc.
• The class user knows how he wants to handle the error. He may want to
  • Exit the program
  • Output a message and continue the program
  • Retry the function that had the error
  • Ask the user what to do
  • Many other possibilities
• The class implementer can't know which of the above actions the user wants to take.
• The class user can't know when an error occurred because the user has no knowledge of the class implemenation.

Exception handling...

• Removes error handling code from the code that caused the error
• Makes it possible to catch all kinds of errors, errors of a certain type, or errors of related types
• Is usually used in situations in which the system can recover.
• Is used when the error will be dealt with by a different part of the program (i.e., different scope) from that which detected the error
• Can be slow, but we don't care because errors occur very infrequently
• Should not be used as an alternative to proper program control