I/O client with command line argument:
ExceptionalClient1.java

These are some fairly common "unchecked exceptions"
• ArrayIndexOutOfBoundsException
  Which occurs when?
• NumberFormatException
  Which occurs when?
Client compiles but when these 'exceptions occur' at runtime
they 'propagate' to the operating system KA-BOOM!!!
 

I/O client with Scanner:
ExceptionalClient2.java

Here are more... fairly common "unchecked exceptions"
• NullPointerException
  Which occurs when?
• InputMismatchException
  Which occurs when?
• IllegalFormatConversionException
  Which occurs when?
Client compiles but when these 'exceptions occur' at runtime
they 'propagate' to the operating system KA-BOOM!!!
 

What's the ANSWER?
How can a programmer 'handle these exceptions'?

• putting in some if-stmt's doesn't really work nicely but what does?
• we could just let them happen and hope user figures it out?
• try/catch
Client compiles but now we have code that 'catches' exceptions BEFORE they 'propagate' to the operating system. This way we can decide how to gracefully 'handle' predictable problems.

This is called "exception handling"
 
 

Terminology / Vocabulary

• exception
• propagation
• throw / throws / thrown
• catch
• handler