HANDLING EXCEPTIONS AND EVENTS - Java Programming: From Problem Analysis to Program Design - page 749

catch (Exception eRef)
{

System.out.println(eRef.toString());

}

}

}

Sample Run: If the input file does not exist, the following message is printed:
java.io.FileNotFoundException: test.txt (The system cannot find the
file specified)
The try block contains statements that open both the input and output files. It also contains
input and output statements. The first catch block catches a FileNotFoundException ,
the second catch block catches all types of exceptions. As shown in the sample run, if
the input file does not exist, the statement in Step 2 in the try block throws a
FileNotFoundException , which is caught and handled by the first catch block.

Rethrowing and Throwing an Exception
When an exception occurs in a try block, control immediately passes to the first
matching catch block. Typically, a catch block does one of the following:
￿ Completely handles the exception.
￿ Partially processes the exception. In this case, the catch block either
rethrows the same exception or throws another exception for the calling
environment to handle the exception.
￿ Rethrows the same exception for the calling environment to handle the
exception.
The catch blocks in Examples 11-3 to 11-6 handled the exception. The mechanism of
rethrowing or throwing an exception is quite useful in cases when a catch block catches
the exception, but the catch block is unable to handle the exception, or if the catch
block decides that the exception should be handled by the calling environment. This
allows the programmer to provide the exception handling code in one place.
Rethrowing an exception or throwing an exception is accomplished by the throw
statement. A throw statement can throw either a checked or an unchecked exception.
Exceptions are objects of a specific class type. Therefore, if you have a reference to an
exception object, you can use the reference to throw the exception. In this case, the
general syntax to rethrow an exception caught by a catch block is:

1
1

throw exceptionReference;