Import multiple classes via java_import

Moving Uwe's comment into description.

I like the first and the last. The second seems a bit too clumsy.

Of the listed alternatives, I like the last as well.

What about:

java_import android.content => [:Context, :Intent], android.view => [:Display, :Gravity]

I think the class names should be allowed to be strings too.

java_import android.content => %w(Context Intent), android.view => %w(Display Gravity)

Nick's suggestion is now my favorite. It can be combined with the first alternative as well:

java_import android.content.Context, android.content.Intent, android.view => [:Display, 'Gravity']

The class names should be allowed to be symbols or strings.

Now for really crazy stuff

java_import android => {:content => %w(Context Intent), :view => %w(Display Gravity)}

This is compatible with Nick's suggestion.

It can surely be an aesthetic preference, but the last one looks ugly to me. It is not immediately clear what classes are imported; I have to look for package hierarchy in multiple and distant places.

I also note that currently support multiple imports via an array:

$ jruby -rjava -S irb
irb(main):001:0> java_import [java.nio.ByteBuffer, java.nio.IntBuffer]
=> nil

Now that I think... it seems to me that java_import should return true when the import is successful.

I think we make java_import explicitly return the class imported for single values. I think the list version was an afterthought and perhaps we should have it return a list of imported classes?

jruby -e 'require "java"; p java_import java.lang.System'
Java::JavaLang::System
jruby -e 'require "java"; p java_import [java.lang.System]'
nil

I like the general concept Uwe is bringing forward, but I am unsure whether we should overload java_import or not...

This change I think is more consistent than what we had with regards to single vs multple arg imports. For people wanting to understand how to write something in both 1.6.x and 1.7.x+ and expect it to work in both:

*list = java_import(arg)
*list = java_import [args]

In 1.6.7 the single arg call will return a sngle value which will end up as a list and in 1.7.0 it returns a list which will splat into list. [args] was broken in 1.6, but will not be a list of imports in 1.7.

Ok, main reason for this comment. In 1.6 if I did:

p(java_import "java.lang.System")
p(java_import "java.lang.System")

The second import would return nil to let user know the class has already been loaded (similiar to require). I can see the usefulness of this. For a list of imports I have no clue the best way to preserve that or whether we should preserve this behavior. I will say that the use case of knowing whether something has been loaded should be simple (perhaps just defined? Java::java.lang.System???).

Uwe is spec'ing the return values with what we have committed on master now, but we should perhaps discuss whether we are really done or not for this feature.