Pass a Ruby block to a Java method

Question

I need my JRuby method to recieve a report of what is going on in a Java method and act accordingly:

def my_long_running_method
  # ... do stuff ...

  jObject.count_all_disk_files do |number_of_files|
    stream.write "#{number_of_files} files found so far."
  end

  # ... do more stuff ...
end

I saw this question but I couldn't understand what I need to do.

I've known Ruby for a long time and a little of Java. This project needs to be JRuby because of old Java code that needs to be integrated with new Ruby code.

Answer 1

For a complete reference, see the Calling Java From JRuby wiki page , specifically the section about closure conversion . The short answer to your question is that your Java method count_all_disk_files will need to accept an interface with a single method (a "functional interface"). Then JRuby will be able to automatically implement that interface with the code from the block.