Because Collections don't allow init values to be declared during construction,
actual implementation code would have to be generated. Not sure we want to do
this, or how we would want to do this since there are multiple ways to do it.
Probably the simplest way would be in a instance initialize block:

for example:
private ArrayList<String> foo = new ArrayList<String>();
{
    foo.add("one");
    foo.add("two");
}

Or, in the constructor... but which constructor if more than one?

If member is static, then code would need to be gen'ed into the static init block.

Or, we could just ignore the initial values when using Collection overriding.

The instance initialize block and static init block are enough to
initialize a collection. 
I could suggest the following pattern:

-------------------------------------------------------------
  private ArrayList<String> foo = new ArrayList<String>();
  {
      for( String value: new String [] {"1", "2", "3"} ){
          foo.add(value);
      }
  }
-------------------------------------------------------------

problem still exists in new code gen module

support for advanced initial values is more like enhancement, currently it's just like literal/string value