JRuby Reference

`snark`

require 'path/to/file.jar'

require can take a path to a jar file. It searches the JRuby $LOAD_PATH for the file.

require 'java'

A special `require 'java'` directive in your file will give you access to any bundled Java libraries (classes within your java class path). However, this will not give you access to any non-bundled libraries.

#each

JRuby supports calling the `#each` method on Enumerable objects

Name translations

Java: org.foo.department.Widget

Ruby: Java::OrgFooDepartment::Widget

For the top-level Java packages java, javax, org, and com you can type in a fully qualified class name:

java_import java.lang.System

You can use your own top-level package names by adding a def:

def edu
  Java::Edu
end

java_import edu.example.MyClass

Importing a package into a class or module

module M
 include_package "org.xxx.yyy"
 # now any class within "org.xxx.yyy" will be available within
 # this module, ex if "org.xxx.yyy.MyClass" exists
 # a = MyClass.new
end

Note that there are issues with include_package, discussed at http://jira.codehaus.org/browse/JRUBY-5558.

enums

Available as constants:

ms_constant_value = java.util.concurrent.TimeUnit::MILLISECONDS