PROPOSAL: Return 'this'

Tom Hawtin Thomas.Hawtin at Sun.COM
Thu Mar 26 08:03:53 PDT 2009

Marek Kozieł wrote:

> Simplification of “return this” statement.
> 'void' can be easy replaced with 'this'.
> MAJOR BENEFIT(s): It would prevent NullPointerException, and make some
> 'builder' like interfaces look really clear and simple.

My problem with this is that it is an attempt to fix a hack due to a 
language problem with a language hack.

The underlying problem is that Java does not have a concise syntax for 
builders. The usual hack is for builders to return this and clients to 
use method chaining. This solution makes the hack easier. A better 
solution would be direct, explicit support for builders in some form.

Also the variant of this proposal that client-side reinterprets 
returning void to return this, would interfere to some extent with 
covariantly returning void when overriding a return of Void.

Tom Hawtin

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