Try to implement java.util.concurrent.CountDownLatch in Ruby

count_down_latch.rb

class CountDownLatch
  def initialize(count)
    raise ArgumentError, 'count < 0' if count < 0
    @count = count
    @lock = Monitor.new
    @condition = @lock.new_cond
  end

  def count_down
    @lock.synchronize do
      @count -= 1 if @count > 0
      @condition.broadcast if @count == 0
    end
  end

  def await
    @lock.synchronize do
      @condition.wait if @count > 0
    end
  end
end