Java Reference
In-Depth Information
The
finally
block is used when we want to execute something at the end regardless
of whether an exception occurred or not. This can include, for example, closing a file or
freeing resources.
Next, we will present an example code that can raise multiple exceptions.
import
java . util .
∗
;
public class
Test
{
public static void
main(String args [])
{
while
(
true
)
{
try
{
Scanner console =
new
Scanner(System. in) ;
System. out . print (
"Enter a number: "
);
int
i=console.nextInt();
if
(i % 2 == 0)
{
throw new
EvenException() ;
break
;
}
catch
(InputMismatchException e)
{
System. out . println (
"Not a number! Try again!"
);
}
catch
(EvenException e)
{
System. out . println (
"Number is even! Try again!"
);
}
catch
(Exception e)
{
System. out . println (
"Something went wrong! Try again!"
);
}
}
}
}
class
EvenException
extends
Exception
{
public
EvenException()
{
super
(
"Even number exception"
);
}
}
First, note that we created our own exception class. As expected, our exception class
inherits from the
Exception
class. The constructor passes the name of the exception to the
Exception
superclass. Next, let us examine the
main
method. An
InputMismatchException
will be generated if an integer is not entered. Similarly, an
EvenException
will be generated
when an even integer is entered. The
throw
keyword is used to generate a new exception.
Our code has three
catch
statements: if the user enters something that is not an integer, if
the user enters an even number, and if something else goes wrong.
Extra care should be taken in the ordering of the
catch
blocks. We should always
order them from the most specific exception to the most general exception.
If
catch(Exception e)
was the first exception, then there is no chance that another
catch
block will be executed. When an exception object is generated, Java checks the first
catch
statement. If the exception object does not belong to the exception class in the first
catch
statement, then
Java
proceeds to the next
catch
statement and so on. On a side
note, if the
check
blocks are not ordered correctly from the most specific one to the most
general one, the program will simply not compile.
