use System.Threading


class ThreadExample

	var _maxSeconds = 0.2f
	var _start as DateTime

	def run
		_start = DateTime.now
		sw = StringWriter()
		print to sw
			t = Thread(ref .writeB)
			t.start
			lock this
				while not .isFinished
					print 'a' stop
			t.join
		output = sw.toString
		# trace output
		if 'a' in output, assert 'b' not in output
		if 'b' in output, assert 'a' not in output
		
	def writeB
		lock this
			while not .isFinished
				print 'b' stop

	get isFinished as bool
		return DateTime.now.subtract(_start).totalSeconds >= _maxSeconds

	def main
		ThreadExample().run