Is nil coerced to null when calling Java from JRuby?

Question

https://github.com/jruby/jruby/wiki/CallingJavaFromJRuby indicates that the Java null object is coerced to Ruby's nil, but it doesn't mention if coercion occurs in the other direction (e.g. when an argument is passed to a Java method). Does it? If not, how can you create null from JRuby?

I did note that nil.to_java returns nil.

Answer 1

To clarify, the answer to your question is yes.

To see this for yourself, just try passing nil to any Java method and see what happens, it's pretty easy to do:

> java.lang.System.out.println(nil)
null
 => nil

Or

> java.lang.String.new(nil)
Java::JavaLang::NullPointerException:

Answer 2

Try

  JavaUtil.primitive_to_java(nil)