Problem with method references

Brian Goetz brian.goetz at
Fri Jan 14 09:44:15 PST 2011

> If we follow method/constructor invocation syntax as closely as possible, existing Java developers would grasp the syntax more quickly.
> The only conceptual addition to method/constructor invocation syntax is prefixing instance method / inner class constructor with declaring / enclosing class name:
>    DeclaringClassName#instanceMethod
>    EnclosingClassName#new InnerClass;
> ... to construct a function that takes an additional 1st argument being an instance of declaring/enclosing class. These two forms have no analogous counterparts as method/constructor invocations so their syntax does not associate to any known concept.

The bytecode would disagree :)

Inner class constructors show up as constructors that take an outer 
argument.  For a class:

public class Outer {
   public class Inner {

the inner class bytecode looks like

public class Outer$Inner extends java.lang.Object{
   final Outer this$0;

   public Outer$Inner(Outer);

Which means the syntax Inner#new works fine for inner class instances 
too -- if you know about the secret first Outer argument.

Given that this is at least a CC^2 (corner case of a corner case) or 
even a CC^3, I think we don't want to create new syntax for this. 
(Quiz: what percentage of Java developers have used the 
Inner() syntax?)

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