Exception Handling - Java - page 476

This catch block looks very much like a method definition that has a parameter of
a type Exception . It is not a method definition, but in some ways, a catch block is like
a method. It is a separate piece of code that is executed when your program encounters
(and executes) the following (within the preceding try block):

throw new Exception( Some_String );

So, this throw statement is similar to a method call, but instead of calling a method,
it calls the catch block and says to execute the code in the catch block. A catch block
is often referred to as an exception handler .
Let's focus on the identifier e in the following line from a catch block:

exception
handler

catch (Exception e)

That identifier e in the catch block heading is called the catch block parameter .
Each catch block can have at most one catch block parameter. The catch block
parameter does two things:
1. The catch block parameter is preceded by an exception class name that specifies what
type of thrown exception object the catch block can catch.
2. The catch block parameter gives you a name for the thrown object that is caught,
so you can write code in the catch block that does things with the thrown object
that is caught.
Although the identifier e is often used for the catch block parameter, this is not
required. You may use any non-keyword identifier for the catch block parameter just
as you can for a method parameter.

catch block
parameter

catch Block Parameter
The catch block parameter is an identifier in the heading of a catch block that serves as a
placeholder for an exception that might be thrown. When a (suitable) exception is thrown in
the preceding try block, that exception is plugged in for the catch block parameter. The
identifier e is often used for catch block parameters, but this is not required. You can use any
legal (non-keyword) identifier for a catch block parameter.
SYNTAX
catch ( Exception_Class_Name Catch_Block_Parameter )
{
< Code to be performed if an exception of the named exception class
is thrown in the try block. >

}

You may use any legal identifier for the Catch_Block_Parameter .