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Difference Between Throw and Throws.

Mahi Ranga
Ranch Hand

Joined: Jan 27, 2011
Posts: 35
Hi,

what is the difference between throw and throws? and when can i use throw and when can i use throws.
Please tell me.
Advanced thanks for your Answer.

Regards,
MahiRanga.
James Hodgkiss
Ranch Hand

Joined: Jan 22, 2004
Posts: 401
Hiya MahiRanga,



Hope that helps!

Cheers,
James
Stephan van Hulst
Bartender

Joined: Sep 20, 2010
Posts: 3602
    
  14

You use throws in a method signature to indicate that a method is capable of throwing a particular exception. Any code calling this method will have to deal with the possibility that that particular exception can occur.

The throw keyword is used to actually throw an exception. It can be used wherever you can place a statement.

[eta]

In James' above example, any code that calls checkString() will have to deal with the fact that it *can* throw an exception, and checkString() actually throws an exception if the argument is null.
fred rosenberger
lowercase baba
Bartender

Joined: Oct 02, 2003
Posts: 11168
    
  16

"throw" is a command. "Mahi, throw the ball". I am telling you to do something.

"throws" is used to describe something. "Mahi throws a curveball, a fastball, and a slider". I'm telling someone what you can do (or will potentially do in the future).

In java, 'throws' is used to tell the compiler what kind of exceptions a method might pass back up to the caller.

"throw" is used to tell the JVM "hey, you need to send this up to the caller NOW".


There are only two hard things in computer science: cache invalidation, naming things, and off-by-one errors
Campbell Ritchie
Sheriff

Joined: Oct 13, 2005
Posts: 38045
    
  22
To the Batmobile . . . er . . . Java™ Tutorials!
Vas Miriyala
Ranch Hand

Joined: Sep 14, 2009
Posts: 114

Nice explanation guys,thanks for all your answers.
Campbell Ritchie
Sheriff

Joined: Oct 13, 2005
Posts: 38045
    
  22
You're welcome
 
It is sorta covered in the JavaRanch Style Guide.
 
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