Re-namespacing a bit to clear out some fairly old stuff from the top level

oldstuff/RubyFun/koans/about_java_interop.rb

@@ -0,0 +1,137 @@
+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_array.class
+  end
+
+  def test_java_class_can_be_referenced_using_both_ruby_and_java_like_syntax
+    assert_equal __, 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 __, 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_string.class
+    assert_equal __, JString
+  end
+
+  def test_can_directly_call_java_methods_on_java_objects
+    java_string = JString.new("A Java String")
+    assert_equal __, java_string.toLowerCase
+  end
+
+  def test_jruby_provides_snake_case_versions_of_java_methods
+    java_string = JString.new("A Java String")
+    assert_equal __, 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 __, java_string.endsWith("String")
+    assert_equal __, java_string.ends_with("String")
+    assert_equal __, 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 __, java_string.is_a?(java.lang.String)
+    assert_equal __, 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 __, ruby_string == java_string
+    assert_equal __, java_string == ruby_string
+
+    # THINK ABOUT IT:
+    #
+    # Is there any possible way for this to be more wrong?
+    #
+    # SERIOUSLY, THINK ABOUT IT:
+    #
+    # Why do you suppose that Ruby and Java strings compare like that?
+    #
+    # ADVANCED THINK ABOUT IT:
+    #
+    # Is there a way to make Ruby/Java string comparisons commutative?
+    # How would you do it?
+  end
+
+  def test_however_most_methods_returning_strings_return_ruby_strings
+    java_array = java.util.ArrayList.new
+    assert_equal __, java_array.toString
+    assert_equal __, java_array.toString.is_a?(String)
+    assert_equal __, java_array.toString.is_a?(java.lang.String)
+  end
+
+  def test_some_ruby_objects_can_be_coerced_to_java
+    assert_equal __, "ruby string".to_java.class
+    assert_equal __, 1.to_java.class
+    assert_equal __, 9.32.to_java.class
+    assert_equal __, false.to_java.class
+  end
+
+  def test_some_ruby_objects_are_not_coerced_to_what_you_might_expect
+    assert_equal __, [].to_java.class == Java::JavaUtil::ArrayList
+    assert_equal __, {}.to_java.class == Java::JavaUtil::HashMap
+    assert_equal __, Object.new.to_java.class == Java::JavaLang::Object
+  end
+
+  def test_java_collections_are_enumerable
+    java_array = java.util.ArrayList.new
+    java_array << "one" << "two" << "three"
+    assert_equal __, java_array.map { |item| item.upcase }
+  end
+
+  # ------------------------------------------------------------------
+
+  # Open the Java ArrayList class and add a new method.
+  class Java::JavaUtil::ArrayList
+    def multiply_all
+      result = 1
+      each do |item|
+        result *= item
+      end
+      result
+    end
+  end
+
+  def test_java_class_are_open_from_ruby
+    java_array = java.util.ArrayList.new
+    java_array.add_all([1,2,3,4,5])
+
+    assert_equal __, java_array.multiply_all
+  end
+
+end