Example JRuby program to display the JVM's available locales and their number, currency, and date formats. Change the format constants to see more kinds of formatting (e.g. DateFormat::LONG/SHORT). - Keith R. Bennett, @keithrbennett

locale_displayer.rb

# Example JRuby program to display the JVM's available locales
# and their number, currency, and date formats.
#
# Keith R. Bennett, @keithrbennett

require 'java'

java_import 'java.util.Locale'
java_import 'java.text.DateFormat'
java_import 'java.text.NumberFormat'


class NumberFormat
  java_alias :format_double, :format, [Java::double]
end

class LocaleDisplayer

  class LocaleData
    
    attr_reader :java_locale, :number_formatter, :currency_formatter, :date_time_formatter
  
    def initialize(java_locale)
      @java_locale = java_locale
      setup_formatters
    end

    def setup_formatters
      
      @date_time_formatter = java.text.DateFormat.java_send(:getDateTimeInstance,
          [Java::int, Java::int, Locale],
           DateFormat::MEDIUM, DateFormat::MEDIUM, java_locale)
      @number_formatter = NumberFormat.java_send(:getInstance, [Locale], java_locale)
      @currency_formatter = NumberFormat.java_send(:getCurrencyInstance, [Locale], java_locale)
    end
    
    def format_number(number)
      number_formatter.format_double(number)
    end
    
    def format_currency(number)
      currency_formatter.format_double(number)
    end
  
    def format_date(date)
      date_time_formatter.format(date)
    end
  
    def display_name
      java_locale.display_name
    end
    
    def code
      java_locale.toString
    end
  
  end

  def format_string
    "%-12.12s  %-20.20s     %-30.30s     %-17.17s     %-17.17s\n"
  end
  
  def header_line
    format_string % ['Code', 'Description', 'Date Format', 'Number Format', 'Currency Format']
  end

  def data_line(locale_data)
    format_string % [
        locale_data.code,
        locale_data.display_name, 
        locale_data.format_date(java.util.Date.new),
        locale_data.format_number(java.lang.Double.new(1234567.89)), 
        locale_data.format_currency(java.lang.Double.new(1234567.89)), 
    ]
  end
  
  def all_locales
    @all_locales ||=
      Locale.available_locales.sort do |locale_1, locale_2|
        locale_1.display_name <=> locale_2.display_name
      end
  end
    
  def print_all(out = STDOUT)
    out << header_line << "\n"
    all_locales.each { |locale| out << data_line(LocaleData.new(locale)) }
  end
  
end

LocaleDisplayer.new.print_all