JRuby programs

jruby01.rb

# First get the current local time
t = Time.now
# to get day, month and year with century
# also hour, minute and second
puts t.strftime("%d/%m/%Y %H:%M:%S")

# You can use the upper case A and B to get the full
# name of the weekday and month, respectively
puts t.strftime("%A") 
puts t.strftime("%B")

# You can use the lower case a and b to get the abbreviated 
# name of the weekday and month, respectively
puts t.strftime("%a") 
puts t.strftime("%b")

# 24 hour clock and Time zone name
puts t.strftime("at %H:%M %Z")

jruby02.rb

JS = Java::java.lang.System

os   = JS.get_property 'os.name'
home = JS.get_property 'java.home'
mem  = Java::java.lang.Runtime.get_runtime.free_memory

puts "Running on #{os}"
puts "Java home is #{home}"
puts "#{mem} bytes available in JVM"

jruby02m.rb

require 'java'

os   = java.lang.System.get_property 'os.name'
home = java.lang.System.get_property 'java.home'
mem  = java.lang.Runtime.get_runtime.free_memory

puts "Running on #{os}"
puts "Java home is #{home}"
puts "#{mem} bytes available in JVM"

jruby03.rb

require 'java'
#java_import 'java.util.Date'
java_import('java.util.Date') { |pkg,name| 'JDate' }
java_import 'java.text.DateFormat'
date = JDate.new
date_format = DateFormat.get_date_instance
date_us = date_format.format date
puts date_us