Wrapped rcov in a guard so it is bypassed when using JRuby.

Rakefile

@@ -1,7 +1,6 @@
 require 'rubygems'
 require 'rake/testtask'
 require 'rake/rdoctask'
-require 'rcov/rcovtask'
 
 task :default => :test
 
@@ -21,13 +20,6 @@ Rake::RDocTask.new do |rdoc|
   rdoc.options << '--charset' << 'utf-8'
 end
 
-Rcov::RcovTask.new do |t|
-  t.test_files = FileList['test/**/test*.rb'] 
-  t.rcov_opts << "--sort coverage"
-  t.rcov_opts << "--exclude gems"
-  t.rcov_opts << "--no-validator-links"
-end
-
 desc %{Update ".manifest" with the latest list of project filenames. Respect\
 .gitignore by excluding everything that git ignores. Update `files` and\
 `test_files` arrays in "*.gemspec" file if it's present.}
@@ -55,3 +47,15 @@ task :manifest do
   end
   File.open('.manifest', 'w') {|f| f << list.join("\n") }
 end
+
+if RUBY_PLATFORM =~ /java/
+  puts "rcov support disabled (running under JRuby)."
+else
+  require 'rcov/rcovtask'
+  Rcov::RcovTask.new do |t|
+    t.test_files = FileList['test/**/test*.rb'] 
+    t.rcov_opts << "--sort coverage"
+    t.rcov_opts << "--exclude gems"
+    t.rcov_opts << "--no-validator-links"
+  end
+end