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：
* h" p5 ^. \* m  }
! d$ b( O1 s/ f# Q. t public Object buildActions () {
    super.buildActions();
   
    // Create the list of simulation actions. We put these in
    // an action group, because we want these actions to be
, Y, U6 q- o8 W# P3 P    // executed in a specific order, but these steps should
    // take no (simulated) time. The M(foo) means "The message
    // called <foo>". You can send a message To a particular
    // object, or ForEach object in a collection.
        
; k/ d" k% y( f& J* P+ J: A    // Note we update the heatspace in two phases: first run
0 d9 V; Q! L& M8 v" g. |    // diffusion, then run "updateWorld" to actually enact the
    // changes the heatbugs have made. The ordering here is
    // significant!
" F2 e% y  R' J7 G3 {* v+ G        
    // Note also, that with the additional
    // `randomizeHeatbugUpdateOrder' Boolean flag we can
2 E1 o& Y$ g8 B& T9 X    // randomize the order in which the bugs actually run
    // their step rule.  This has the effect of removing any
    // systematic bias in the iteration throught the heatbug
    // list from timestep to timestep
        
    // By default, all `createActionForEach' modelActions have
    // a default order of `Sequential', which means that the
4 i, O) C1 y3 v' K0 s2 t: Z/ x; I    // order of iteration through the `heatbugList' will be
' {/ h5 F# r$ _2 N    // identical (assuming the list order is not changed
8 e, v. H/ H4 l3 \3 s* k    // indirectly by some other process).
   
    modelActions = new ActionGroupImpl (getZone ());
7 ]3 l6 ^1 m& D% G" E
    try {
, [' }  ~# D6 B      modelActions.createActionTo$message
. J7 b( h- H9 l0 [: W        (heat, new Selector (heat.getClass (), "stepRule", false));
' p) f8 u9 f, H% s    } catch (Exception e) {
      System.err.println ("Exception stepRule: " + e.getMessage ());
    }

    try {
      Heatbug proto = (Heatbug) heatbugList.get (0);
      Selector sel =
        new Selector (proto.getClass (), "heatbugStep", false);
      actionForEach =
# T2 p' z4 N; V- w  S6 \0 t        modelActions.createFActionForEachHomogeneous$call
8 U- o/ F" c# @: x6 k1 [8 k        (heatbugList,
9 w3 L- v/ G6 D, c. [! K2 f/ W         new FCallImpl (this, proto, sel,
1 A4 H4 e; n8 A                        new FArgumentsImpl (this, sel)));
6 @; ]8 j- v) e; G# s# x- @    } catch (Exception e) {
) R8 s! J% i, T" y      e.printStackTrace (System.err);
- _4 E/ c$ H. z- q& e5 D) h; O    }
   
: M& `$ S, H* F2 A, N- R    syncUpdateOrder ();
7 }% {( h/ V4 S5 C
: i* E2 u5 f0 Y" W    try {
) t% q0 Z- {2 i& Q" K5 |" ~      modelActions.createActionTo$message
        (heat, new Selector (heat.getClass (), "updateLattice", false));
    } catch (Exception e) {
+ ^0 o1 {. U8 @% h- }* v+ @0 _      System.err.println("Exception updateLattice: " + e.getMessage ());
- a' M% L; t, }9 M* I8 n" M    }
5 f2 z9 M# R, ]0 N  j( n        
3 ^' K3 ]4 w6 }0 r: l/ Z    // Then we create a schedule that executes the
    // modelActions. modelActions is an ActionGroup, by itself it
7 `' {, y# T# V6 |! n    // has no notion of time. In order to have it executed in
; i  B7 A3 R- {, T2 D& _    // time, we create a Schedule that says to use the
  J& w0 b, D5 }% a5 V    // modelActions ActionGroup at particular times.  This
    // schedule has a repeat interval of 1, it will loop every
    // time step.  The action is executed at time 0 relative to
    // the beginning of the loop.
* ]+ O% z0 _& F( ]8 x
) E; a2 f7 S3 e/ ]! ?: [    // This is a simple schedule, with only one action that is
    // just repeated every time. See jmousetrap for more
    // complicated schedules.
& @. u( J  n3 d0 ?5 }8 x& I6 M  
    modelSchedule = new ScheduleImpl (getZone (), 1);
    modelSchedule.at$createAction (0, modelActions);
( t1 P& a" i9 D& x        
    return this;
  }