require 'monitor'
class Counter < Monitor
attr_reader :count
def initialize
@count = 0
super
end
def tick
synchronize do
@count += 1
end
end
end
c = Counter.new
t1 = Thread.new { 10000.times { c.tick } }
t2 = Thread.new { 10000.times { c.tick } }
t1.join; t2.join
c.count # 20000