Exception Handling - Absolute Java - page 527

EXAMPLE
In the following, e is the catch block parameter.
catch (Exception e)
{
System.out.println(e.getMessage());
System.out.println("Aborting program.");
System.exit(0);
}
Let's consider two possible cases of what can happen when a try block is executed:
(1) no exception is thrown in the try block, and (2) an exception is thrown in the
try block and caught in the catch block. (Later in the Tip, “What Happens if an
Exception Is Never Caught?,” we will describe a third case where the catch block does
not catch the exception.)
• If no exception is thrown, the code in the try block is executed to the end of the
try block, the catch block is skipped, and execution continues with the code placed
after the catch block.
• If an exception is thrown in the try block, the rest of the code in the try block
is skipped and (in simple cases) control is transferred to a following catch block.
The thrown object is plugged in for the catch block parameter, and the code in
the catch block is executed. And then (provided the catch block code does not
end the program or do something else to end the catch block code prematurely), the
code that follows that catch block is executed.
Exception Handling with the Scanner Class
As a concrete example, consider a program that reads an int value from the keyboard
using the nextInt method of the Scanner class. You have probably noticed that
the program will end with an error message if the user enters something other than
a well-formed int value. That is true as far as it goes, but the full detail is that
if the user enters something other than a well-formed int value, an exception of
type InputMismatchException will be thrown. If the exception is not caught, your
program ends with an error message. However, you can catch the exception, and
in the catch block, give code for some alternative action, such as asking the user to
reenter the input. You are not required to account for an InputMismatchException
by catching it in a catch block or declaring it in a throws clause (this is because
InputMismatchException is a descendent class of RuntimeException ). However,
you are allowed to catch an InputMismatchException in a catch block, which can
sometimes be useful.