ALLU

Checked exceptions:

• represent invalid conditions in areas outside the immediate control of the program (invalid user input, database problems, network outages, absent files)
• are subclasses of Exception
• methods are obliged to establish a policy for all checked exceptions thrown by its implementation (either pass the checked exception further up the stack, or handle it somehow)

Unchecked exceptions:

• represent defects in the program (often invalid arguments passed to a non-private method)
• are subclasses of RuntimeException, and are usually implemented using IllegalArgumentException, NullPointerException, or IllegalStateException
• methods are not obliged to establish a policy for the unchecked exceptions thrown by its implementation (and they almost always do not do so)

It is somewhat confusing, but note as well that RuntimeException (unchecked) is itself a subclass of Exception (checked).