Design for collections upgrades

Brian Goetz brian.goetz at
Tue Mar 8 10:36:48 PST 2011

> Very nice. I'm curious about the exception declaration in the
> streaming model.

This is an open issue.  There is an outline for Exception Transparency 
linked from the latest State of the Lambda that outlines one possible 
approach which would play nicely with checked exceptions, at the cost of 
some complexity (in the form of more pointy-bracket craziness (though 
hopefully mostly inferred by the compiler)).  An alternative that some 
have suggested is to define the standard SAM types to throw nothing, and 
let lambdas use unchecked exceptions.  (The difference between the two 
is the age-old checked-vs-unchecked exceptions debate.)

Both are credible alternatives; most filter/map/reduce lambdas will not 
throw checked exceptions (though forEach lambda arguments might well, 
since that relies on side-effects to do anything.)  Stay tuned.

> Also, would you consider adding list comprehension syntax, which would
> de-sugar to the serial/eager version:

I'll be honest: no chance of this for Java 8.  And not on the radar for 
after that, either.  Our approach to language evolution here is to add 
the features needed to support library evolution.

More information about the lambda-dev mailing list