--- /dev/null
+require File.expand_path(File.dirname(__FILE__) + '/edgecase')
+
+include Java
+
+# Concepts
+# * Pull in a java class
+# * calling a method, Camel vs snake
+# * Resovling module/class name conflicts
+# * Showing what gets returned
+# * Ruby Strings VS Java Strings
+# * Calling custom java class
+# * Calling Ruby from java???
+
+class AboutJavaInterop < EdgeCase::Koan
+ def test_using_a_java_library_class
+ java_array = java.util.ArrayList.new
+ assert_equal __(Java::JavaUtil::ArrayList), java_array.class
+ end
+
+ def test_java_class_can_be_referenced_using_both_ruby_and_java_like_syntax
+ assert_equal __(true), Java::JavaUtil::ArrayList == java.util.ArrayList
+ end
+
+ def test_include_class_includes_class_in_module_scope
+ assert_nil defined?(TreeSet) # __
+ include_class "java.util.TreeSet"
+ assert_equal __("constant"), defined?(TreeSet)
+ end
+
+ # THINK ABOUT IT:
+ #
+ # What if we use:
+ #
+ # include_class "java.lang.String"
+ #
+ # What would be the value of the String constant after this
+ # include_class is run? Would it be useful to provide a way of
+ # aliasing java classes to different names?
+
+ JString = java.lang.String
+ def test_also_java_class_can_be_given_ruby_aliases
+ java_string = JString.new("A Java String")
+ assert_equal __(java.lang.String), java_string.class
+ assert_equal __(java.lang.String), JString
+ end
+
+ def test_can_directly_call_java_methods_on_java_objects
+ java_string = JString.new("A Java String")
+ assert_equal __("a java string"), java_string.toLowerCase
+ end
+
+ def test_jruby_provides_snake_case_versions_of_java_methods
+ java_string = JString.new("A Java String")
+ assert_equal __("a java string"), java_string.to_lower_case
+ end
+
+ def test_jruby_provides_question_mark_versions_of_boolean_methods
+ java_string = JString.new("A Java String")
+ assert_equal __(true), java_string.endsWith("String")
+ assert_equal __(true), java_string.ends_with("String")
+ assert_equal __(true), java_string.ends_with?("String")
+ end
+
+ def test_java_string_are_not_ruby_strings
+ ruby_string = "A Java String"
+ java_string = java.lang.String.new(ruby_string)
+ assert_equal __(true), java_string.is_a?(java.lang.String)
+ assert_equal __(false), java_string.is_a?(String)
+ end
+
+ def test_java_strings_can_be_compared_to_ruby_strings_maybe
+ ruby_string = "A Java String"
+ java_string = java.lang.String.new(ruby_string)
+ assert_equal __(false), ruby_string == java_string
+ assert_equal __(true), java_string == ruby_string
+
+ # THINK ABOUT IT:
+ # Is there any possible way for this to be more wrong?
+ end
+
+ def test_however_most_methods_returning_strings_return_ruby_strings
+ java_array = java.util.ArrayList.new
+ assert_equal __("[]"), java_array.toString
+ assert_equal __(true), java_array.toString.is_a?(String)
+ assert_equal __(false), java_array.toString.is_a?(java.lang.String)
+ end
+
+
+end