I am glad that you mention named constructors! I learned to love them in Smalltalk and Newspeak, and only left them out in this post to avoid confusing the uninitiated reader with two new concepts at once. Java’s new keyword is terribly limited, and “injection is the new new” can’t be the solution either. Named constructors are awesome! Also, passing a block to them (that receives an inner builder class as argument) even offers a nice way to implement a small builder DSL …hmm, mebbe that should go into a post if its own :)

Nice post; one more point I’d like to make:

When you use a special syntax like new Foo(x) to instantiate classes, you’re restricting yourself. Say you want to look up instances in a cache, rather than allocating fresh ones. You would like to replace the class Foo with an object that looks up instances in the cache (say, based on the value of x, the argument to the constructor. That is why it is important to do away with traditional constructors even when classes are virtual. Therefore, in Newspeak, constructors (aka factories) have names and their use is indistinguishable from ordinary methods.

sub foo {
 ...
 return FriendClass->new->something(@xyz);
}

we write

sub foo {
  ...
  return $self->friendclass->new->something(@xyz);
}

sub friendclass { 'FriendClass' }

And yeah, this does the trick nicely.