HB.scala

// Does the Java memory model guarantee that this program will *always* print
//    x=1 and y=2
//
//Or might the JVM decide that the changes made to x and y in t2 do not need to be visible from t1 because neither x nor 
// y is volatile and nor are they modified within a sychronized block (or within the confines of a j.u.c Lock)? 
// i.e. I am unsure whether you can observe 
//    x=0 and y=0

//
//I believe that the memory model *definitely makes the guarantee* that t1 will *never* print something like:
//    x=0 and y=2
//

object HB extends App {
  @volatile var v = true
  var x = 0
  var y = 0
  
  val t1 = new Thread {
    override def run(): Unit = {
      while (v) {
        Thread.sleep(10L)
      }
      println(s"x=$x and y=$y")
    }
  }

  
  val t2: Thread = new Thread {
    override def run(): Unit = {
      x = 1
      y = 2
      v = false
    }
  }
  t1.start()
  t2.start()
  t1.join()
  t2.join()
}