Difficulty understanding this for loop...

[Ravaa Bal]

Hi all, I'm working with JavaSound and MIDI right now, and I've got the following conditional which I'm trying to understand:

protected void output(MidiMessage message) {
         for ( Transmitter tx : transmitters ) {
             tx.getReceiver().send(message, -1);
         }
     }

Now the part which I mainly don't understand is the "Transmitter tx : transmitters" part. What does that colon do?

Here's the 'full' code:

public class AccompanimentMidiDevice implements MidiDevice

{
     private List<Receiver> receivers = new ArrayList<Receiver>();
     private List<Transmitter> transmitters = new ArrayList<Transmitter>();

protected void output(MidiMessage message) {
         for ( Transmitter tx : transmitters ) {
             tx.getReceiver().send(message, -1);
         }
     }

Thank you kindly.

[fred rosenberger]

it's what is called the 'enhanced for loop' or the 'for each' loop.

transmitters is some kind of collection that holds Transmitter objects. so this basically means

'For each Transmitter tx in transmitters...'

it iterates across every object in the collection, and runs them through the body of the loop.

[ani pillai]

You might want to go through this for a better grip on the enhanced for loop syntax

http://java.sun.com/j2se/1.5.0/docs/guide/language/foreach.html

[Ravaa Bal]

Thank you both, that makes sense!