Call by name VS call by value in Scala

ByNameValue.scala

// defining a simple function that returns the current time
def getTime = System.currentTimeMillis

// defining a function, by NAME, that prints two times: now and one second later
def getTimeByName(f: => Long) = { println(f); Thread.sleep(1000); println(f)}

// defining it again, but this time, by VALUE
def getTimeByValue(f: Long) = { println(f); Thread.sleep(1000); println(f)}

getTimeByName(getTime)
// prints:
// 1514451008323
// 1514451009325

getTimeByValue(getTime)
// prints:
// 1514451024846
// 1514451024846