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：
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, Y+ I/ t& q! V5 o2 o% ^ public Object buildActions () {
, Y  I% [3 F/ x: J    super.buildActions();
5 B% @; s5 m  l- e  K   
8 J) L+ w  j$ ~6 p& G; C/ r3 d    // Create the list of simulation actions. We put these in
    // an action group, because we want these actions to be
' u  _; t* L. K- l( t* S    // executed in a specific order, but these steps should
& k, i* s$ b& m; T: o    // take no (simulated) time. The M(foo) means "The message
5 P; V; }5 F; f& A" g$ B7 f    // called <foo>". You can send a message To a particular
    // object, or ForEach object in a collection.
        
    // Note we update the heatspace in two phases: first run
    // diffusion, then run "updateWorld" to actually enact the
    // changes the heatbugs have made. The ordering here is
8 m- [0 ^8 J6 s6 p# _5 p2 g$ [    // significant!
        
    // Note also, that with the additional
    // `randomizeHeatbugUpdateOrder' Boolean flag we can
    // randomize the order in which the bugs actually run
4 Z9 s) r$ N. `+ u( j    // their step rule.  This has the effect of removing any
    // systematic bias in the iteration throught the heatbug
& U2 o5 i; @% X+ o$ S    // list from timestep to timestep
        
    // By default, all `createActionForEach' modelActions have
    // a default order of `Sequential', which means that the
    // order of iteration through the `heatbugList' will be
) v$ s" m3 y% a2 X    // identical (assuming the list order is not changed
    // indirectly by some other process).
   
0 Y6 X+ G5 a8 U  ]    modelActions = new ActionGroupImpl (getZone ());

    try {
; B5 U: l$ a/ c0 [      modelActions.createActionTo$message
        (heat, new Selector (heat.getClass (), "stepRule", false));
8 p) t' m. s6 ~0 s, {2 E( x$ {# M    } catch (Exception e) {
      System.err.println ("Exception stepRule: " + e.getMessage ());
" A4 n; X) W7 r# {$ @2 ^    }

    try {
8 S" q! h- X: X/ w7 L- P2 F) b      Heatbug proto = (Heatbug) heatbugList.get (0);
      Selector sel =
6 A: k0 \. {* A8 N        new Selector (proto.getClass (), "heatbugStep", false);
      actionForEach =
        modelActions.createFActionForEachHomogeneous$call
' p$ D, }5 T3 Z, t* y% G        (heatbugList,
         new FCallImpl (this, proto, sel,
' X2 {4 K9 P" `. I& @' U8 p                        new FArgumentsImpl (this, sel)));
    } catch (Exception e) {
      e.printStackTrace (System.err);
    }
   
    syncUpdateOrder ();
8 \5 u/ V. J$ S" N2 j6 u
    try {
      modelActions.createActionTo$message
4 z) O4 ~# {% `, P" L( n6 E        (heat, new Selector (heat.getClass (), "updateLattice", false));
    } catch (Exception e) {
      System.err.println("Exception updateLattice: " + e.getMessage ());
! H' n0 v4 z, ~3 }5 s/ k    }
        
    // Then we create a schedule that executes the
    // modelActions. modelActions is an ActionGroup, by itself it
    // has no notion of time. In order to have it executed in
    // time, we create a Schedule that says to use the
* b& j9 M# S) B( G    // modelActions ActionGroup at particular times.  This
$ i" w; ^3 t  f, l& ?0 C. G; b" S    // schedule has a repeat interval of 1, it will loop every
    // time step.  The action is executed at time 0 relative to
6 P/ \) n4 j5 g5 T/ ?) z    // the beginning of the loop.
2 K7 ]( ?+ T# G5 V2 R& @9 q
% Z5 H3 v& X+ P0 y    // 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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  B7 H: F! l% w% I+ p% o    modelSchedule = new ScheduleImpl (getZone (), 1);
+ B5 R7 n2 X, u) V6 n; }    modelSchedule.at$createAction (0, modelActions);
1 r3 \% w8 q2 r* j+ t        
    return this;
  }