For unchecked Exceptions ( i.e. Errors and RuntimeExceptions such as IllegalArgumentException) the throws clause is optional. I find them useful documentation since they show up in the Javadoc.

Sample Code

String myMethod()
   {
   try
      {
      return trickyMethod();
      }
   catch ( IOException e )
      {
      return null;
      }
   }

String trickyMethod() throws IOException
{
   int result = readAnotherChar();
   if ( result < 0 ) throw new IOException( "bad data" );
   return result;
}

Types Of Exception

If you catch RuntimeException you will catch all manner of run time exceptions (type R).
If you catch Error you will catch all manner of errors (type E).
If you catch Exception you will catch all manner of checked exceptions and run time exceptions (type R+C).
If you catch Throwable, you will catch everything, (Type R+E+C );

Table of Specific Exceptions

Missing BadDataFormatException

Rolling Your Own Exception

Status Code or Exception?

• There is nothing that says the caller has check a status code. Programmers are lazy and don’t bother to check return codes. No error or warning is generated.
• If the caller of the caller is the proper place to handle the exception it takes futzing to propagate the information up the chain.
• Exceptions should be exceptional. They are for errors, things that are not supposed happen. EOFException is a special case. It will happen at most once per file. If there are 50/50 odds of either status, you should use a status code. There is an extra overhead to catching an exception. Don’t use Exceptions to return common place data or status. A rule of thumb might be if a method returns an error more often than 1 in 10, use a status code instead of an Exception to report the problem.

Books

	recommend book⇒Java in a Nutshell : A Desktop Quick Reference, Third Edition
		paperback
	ISBN10:	1-56592-487-8
	ISBN13:	978-1-56592-487-1
	publisher:	O’Reilly
	published:	1999-11
	by:	David Flanagan
Author of the classic Java In A Nutshell, now split into three different books Java in a Nutshell : The Desktop Quick Reference, The Java Foundation Classes and Java Examples in a Nutshell. The author answers his email and uses the feedback to improve the book. It has a comprehensive list of exceptions.
amazon.ca amazon.com chapters.indigo.ca powells.com amazon.fr barnesandnoble.com amazon.de O’Reilly Safari amazon.co.uk

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