Java Reference
In-Depth Information
//
// Assume that the source file's extension is RM (for
Real Media) and
// that the file's internal signature suggests that
its format is
// Microsoft WAVE.
String expectedFormat = "RM";
String existingFormat = "WAVE";
throw new InvalidMediaFormatExcep-
tion(expectedFormat, existingFormat);
}
}
sist of class methods and there's no reason to extend it.
Media
's
convert()
method appends
throws InvalidMediaFormatEx-
ception, IOException
to its header. A
throws clause
identifies all checked ex-
ceptionsthatarethrownoutofthemethod,andwhichmustbehandledbysomeother
method. It consists of reserved word
throws
followed by a comma-separated list of
checkedexceptionclassnames,andisalwaysappendedtoamethodheader.The
con-
vert()
method's throws clause indicates that this method is capable of throwing an
InvalidMediaFormatException
or
IOException
instance to the JVM.
convert()
alsodemonstratesthethrowstatement,whichconsistsofreservedword
throw
followedbyaninstanceof
Throwable
orasubclass.(Youtypicallyinstantiate
an
Exception
subclass.)ThisstatementthrowstheinstancetotheJVM,whichthen
searches for a suitable handler to handle the exception.
The first use of the throw statement is to throw a
java.lang.NullPointerException
instancewhenanullreferenceispassedas
the source or destination filename. This unchecked exception is commonly thrown to
sion of the
java.util.Objects
class presents an alternative approach to dealing
withnullreferencespassedtoparameters.)Forexample,youcannotpassnullfilenames
to
convert()
.
The second use of the throw statement is to throw a
me-
dia.InvalidMediaFormatException
instance when the expected media
