Loosen Constructor super()/this() call restrictions (original) (raw)

Joseph D. Darcy Joe.Darcy at Sun.COM
Sun Mar 22 23:25:56 PDT 2009

Hello.

Mike Duigou wrote:

On Mar 22, 2009, at 6:14 PM, Mark Mahieu wrote:

2009/3/23 Jeremy Manson <jeremy.manson at gmail.com> Also, it seems to me that you would want to be careful about access to fields of the parent object before the invocation of super(). Jeremy Yes, which implies no calls to other instance methods, or to static methods passing 'this' as an argument etc. Maybe a simple rule to build upon would be to say that anything before the call to this() or super() is effectively in a static context (ie no references to instance members, or to this/super, are allowed). There'd be more to it than that though. Your clarification is correct. Before the explicit call to super() or this() no reference to instance fields or methods is allowed because the object hasn't been created yet. The case where no explicit call to super/this() is made is a little harder because an implicit call to the no params super() method needs to be inserted before the first reference to an instance field or method in order to construct the object. Also (Mike) there's at least one existing bug entry for this: http://bugs.sun.com/bugdatabase/viewbug.do?bugid=4093999 Hmmm, thanks! That should have been easy to find. Perhaps I searched only open bugs.

While I've certainly chafed at the "must call super first rules," I don't think they are a severe enough annoyance to need addressing by Project Coin.

Additionally, a proposal on this topic should address the sort of points already raised by Jeremy as well as the issues listed in bug 4093999.

-Joe

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