Exception Handling - Absolute Java - page 554

PITFALL: (continued)

catch (NegativeNumberException e)
{
.
.
.
}
With this ordering, the catch block for NegativeNumberException would
never be used, because all exceptions are caught by the first catch block.
Fortunately, the compiler will warn you about this. The correct ordering is to
reverse the catch blocks so that the more specific exception comes before its
parent exception class, as shown in the following:

The second catch block can
never be reached.

catch (NegativeNumberException e)
{
.
.
.
}

catch (Exception e)
{
.
.
.
}

■

Display 9.9 The Class NegativeNumberException

1 public class NegativeNumberException extends Exception
2 {
3 public NegativeNumberException()
4 {
5 super ("Negative Number Exception!");
6 }
7 public NegativeNumberException(String message)
8 {
9 super (message);
10 }
11 }