cucumber_ext.rb

# This file is loaded before Cucumber is loaded.
require 'java'
import 'cuke4duke.Table'
import 'cuke4duke.internal.language.StepMother'

# Workaround to make the java code have access to the same Ruby
# interpreter as the one that is used to run this script.
# org.jruby.Main uses a different instance than what 
# org.jruby.Ruby.getGlobalRuntime() returns. It might be considered
# a JRuby bug.
Java.cuke4duke.internal.JRuby.setRuntime(JRuby.runtime)

class java::util::HashMap
  alias_method :keys, :keySet
end

StuffSteps.java

    @When("I add a table")
    public void iAddATable(Table table) {
    	List<List<String>> diffList = new ArrayList<List<String>>();
    	diffList.add(Arrays.asList("a", "b"));
    	diffList.add(Arrays.asList("1", "2"));
        table.diffLists(diffList);

        List<Map<String, String>> hashes = new ArrayList<Map<String, String>>(table.hashes());
        Map<String, String> newRow = hashes.get(0);
        hashes.add(newRow);
        Map<String, Boolean> hashesMap = new HashMap<String, Boolean>();
        hashesMap.put("surplus_row", false);
        table.diffHashes(hashes, hashesMap);

        hashes = new ArrayList<Map<String, String>>();
        newRow = new HashMap<String, String>();
        newRow.put("a", "1");
        newRow.put("b", "2");
        hashes.add(newRow);
        table.diffHashes(hashes);
    }

table.rb

      def ensure_table(table_or_array) #:nodoc:
        return table_or_array if Table === table_or_array
        table_or_array = hashes_to_array(table_or_array) if table_or_array[0].respond_to? :keys
        table_or_array = enumerable_to_array(table_or_array) unless Array == table_or_array[0]
        Table.new(table_or_array)
      end