output.log

qmx@gondor ~/tmp » jruby threads.rb
starting thread 1
starting thread 0
starting thread 2
starting thread 3
starting thread 4
ending thread 2
ending thread 3
ending thread 1
ending thread 0
ending thread 4
qmx@gondor ~/tmp »

threads.rb

threads = []
5.times do |i|
  threads << Thread.new do
    puts "starting thread #{i}"
    sleep 2
    puts "ending thread #{i}"
  end
end
threads.each do |thread|
  thread.join
end