问jheatbugs-2001-03-28中某些代码

sybbk

HeatbugModelSwarm中buildActions部分，3个try分别是做什么？查了下refbook-java-2.2，解释太简略，还是不懂，高手指点，谢谢！代码如下：
3 o: f) B; N* H+ o  H
public Object buildActions () {
, w2 l% [: W4 Q8 V- i5 ]8 k! s    super.buildActions();
   
6 \  D" ]* V# k* f+ K( L    // Create the list of simulation actions. We put these in
9 |2 W4 [+ d# c6 {6 a! U0 I    // an action group, because we want these actions to be
    // executed in a specific order, but these steps should
/ F3 F. m( x% b/ z8 F3 R+ }    // take no (simulated) time. The M(foo) means "The message
) D: e5 G& S5 p4 ^7 P    // called <foo>". You can send a message To a particular
    // object, or ForEach object in a collection.
        
! [4 K, A9 ]7 N( X5 L0 |  J    // Note we update the heatspace in two phases: first run
    // diffusion, then run "updateWorld" to actually enact the
7 V9 g, n. R& S" `7 @& ~6 @    // changes the heatbugs have made. The ordering here is
4 C1 |; g) Q5 p8 i# @8 b    // significant!
! B# ~3 M3 G2 j7 e& T3 u        
: A" ]' W+ V" S: _( v    // Note also, that with the additional
    // `randomizeHeatbugUpdateOrder' Boolean flag we can
    // randomize the order in which the bugs actually run
' w$ V- V0 R& n. j4 U" ?2 B    // their step rule.  This has the effect of removing any
! ?5 f5 P! X; v5 t1 F( i; V# J( ^  l1 T    // systematic bias in the iteration throught the heatbug
    // list from timestep to timestep
' n4 F7 i# y) Y) Z7 D1 ^        
    // By default, all `createActionForEach' modelActions have
    // a default order of `Sequential', which means that the
  g& n- h& v3 O    // order of iteration through the `heatbugList' will be
, O9 Q! C. j  |5 ~7 g) p    // identical (assuming the list order is not changed
$ ]1 n- y8 l6 a9 R) t: m6 f) z    // indirectly by some other process).
   
    modelActions = new ActionGroupImpl (getZone ());

    try {
      modelActions.createActionTo$message
        (heat, new Selector (heat.getClass (), "stepRule", false));
    } catch (Exception e) {
      System.err.println ("Exception stepRule: " + e.getMessage ());
    }
8 K- R: o# y  @8 p* A0 {
    try {
      Heatbug proto = (Heatbug) heatbugList.get (0);
      Selector sel =
        new Selector (proto.getClass (), "heatbugStep", false);
" r4 U+ h6 _# G      actionForEach =
        modelActions.createFActionForEachHomogeneous$call
2 u! [1 c/ N. l        (heatbugList,
         new FCallImpl (this, proto, sel,
7 y! I! S4 l+ }                        new FArgumentsImpl (this, sel)));
    } catch (Exception e) {
6 F/ ^2 N( p  g      e.printStackTrace (System.err);
    }
   
    syncUpdateOrder ();
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    try {
; j/ ^/ W9 Y0 y' ^& B  @      modelActions.createActionTo$message
        (heat, new Selector (heat.getClass (), "updateLattice", false));
    } catch (Exception e) {
% O2 F* g$ \! t+ v6 {4 L; L; \& O      System.err.println("Exception updateLattice: " + e.getMessage ());
9 d' W  c9 b' Q" X" y4 m, H* J2 [    }
        
    // Then we create a schedule that executes the
    // modelActions. modelActions is an ActionGroup, by itself it
' t7 n9 W) G! D3 y, D6 R2 n- d    // has no notion of time. In order to have it executed in
    // time, we create a Schedule that says to use the
    // modelActions ActionGroup at particular times.  This
    // schedule has a repeat interval of 1, it will loop every
    // time step.  The action is executed at time 0 relative to
9 G( _$ w. H" v4 h+ q! z    // the beginning of the loop.
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1 J5 V: }5 E9 Z; J- D    // This is a simple schedule, with only one action that is
    // just repeated every time. See jmousetrap for more
    // complicated schedules.
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    modelSchedule = new ScheduleImpl (getZone (), 1);
1 _6 z& M! g$ F- r/ f    modelSchedule.at$createAction (0, modelActions);
        
    return this;
  }