Exceptions, Iterators, Iterables

Uncaught Exceptions

• When exception thrown, descends call stack (stack of methods that gets called) if not caught
  • If exceptions reach bottom of stack, program crashes & Java provides message for user

Checked vs Unchecked Exceptions

• Checked exceptions must be handled
  • Compiler requires these to be "caught"/"specified"
    • Goal = prevent avoidable program crashes that could have been handled
• Any subclass of RuntimeException or Error is unchecked
• All other Throwables are checked
• Checked exceptions = part of specification of class

Checking Exceptions

• Specify method as dangerous w/ throws keyword
  • Defers to someone else to handle exception
• If method uses a dangerous method (i.e. might throw checked exception), it becomes dangerous itself

Iteration Intro

• Enhanced for loop/foreach loop = equivalent to iterating through Iterator

Implementing Iterators

• List interface extends Collection extends Iterable interface → inherits abstract iterator() method
• Instantiate non-static nested class (inner class) → use instance.new

Iteration Summary

• Implement Iterable interface to support enhanced for loop
  • iterator() method must return object that implements Iterator interface