Recently, I had the little task of looking at a string and deciding what to do based on the various values of an embedded prefix field.

I had to ask around a bit (thanks Paul!) to get the solution to my liking, but here’s yet another example of my favourite Groovy construct, the switch statement:

def days = [
  "Monday:I could wait till Tuesday",
  "Tuesday:must make up my mind",
  "Wednesday:would be fine",
  "Thursday:she's on my mind",
  "Friday:give me time",
  "Saturday:I could wait",
  "Sunday:would be too late"
]

final MON = 'Monday:'
final TUE = 'Tuesday:'
final WED = 'Wednesday:'
final THU = 'Thursday:'
final FRI = 'Friday:'
final SAT = 'Saturday:'
final SUN = 'Sunday:'

days.each { value ->
  switch(value) {
    case ~/^${MON}.*$/:
      println "$MON: ${value - MON}"
      break
    case ~/^${TUE}.*$/:
      println "$TUE: ${value - TUE}"
      break
    case ~/^${WED}.*$/:
      println "$WED: ${value - WED}"
      break
    case ~/^${THU}.*$/:
      println "$THU: ${value - THU}"
      break
    case ~/^${FRI}.*$/:
      println "$FRI: ${value - FRI}"
      break
    case ~/^${SAT}.*$/:
      println "$SAT: ${value - SAT}"
      break
    case ~/^${SUN}.*$/:
      println "$SUN: ${value - SUN}"
      break
  }
}

I know it’s a very contrived example, but take a look at the case ‘labels’: regular expressions that reference properties found elsewhere in the code. Neat-o!

Apologies to Sting (did you get the song?)!

Just saving this away for a rainy day…something I concocted in response to a question on the Groovy mailing list:

new File("local.gif").withOutputStream { os ->
  new URL("remote.gif").withInputStream { is ->
    os << is
  }
}

The important thing to note here is the way the streams are carefully ’scoped’ and maintained so that no leaks can occur even if exceptions or other sticky situations arise.