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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! F' R. [; b& Q6 Q3 [# q6 u public Object buildActions () {
    super.buildActions();
   
    // Create the list of simulation actions. We put these in
) K: y! `7 K% c' H( B1 R    // an action group, because we want these actions to be
    // executed in a specific order, but these steps should
# b: o0 C! S! \    // 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.
& R  G$ l) [4 @! T* o) J# H        
    // 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
    // significant!
# C$ n1 M: ]. [8 i9 Y        
    // Note also, that with the additional
    // `randomizeHeatbugUpdateOrder' Boolean flag we can
" ?" ?" D1 j; F- p$ Y* o' y    // randomize the order in which the bugs actually run
    // their step rule.  This has the effect of removing any
+ @3 N2 d, P4 ]' s7 a3 ^+ {1 j    // systematic bias in the iteration throught the heatbug
    // list from timestep to timestep
3 J% t: T$ h5 K& b0 A( F        
    // By default, all `createActionForEach' modelActions have
    // a default order of `Sequential', which means that the
6 O0 w/ S) u, s3 z  G; m- ^    // order of iteration through the `heatbugList' will be
    // identical (assuming the list order is not changed
    // indirectly by some other process).
   
+ x; P7 k3 L$ T4 K    modelActions = new ActionGroupImpl (getZone ());
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    try {
      modelActions.createActionTo$message
  M$ U" g2 U+ E3 G% J+ h        (heat, new Selector (heat.getClass (), "stepRule", false));
    } catch (Exception e) {
      System.err.println ("Exception stepRule: " + e.getMessage ());
    }
% {2 E# Y& U6 u0 K" f% t
    try {
$ t9 v) g& C7 r8 o1 q3 c8 {$ a      Heatbug proto = (Heatbug) heatbugList.get (0);
8 A% R4 f  o6 z6 Y' E      Selector sel =
        new Selector (proto.getClass (), "heatbugStep", false);
9 X9 g/ `+ ~$ `: U$ _2 ~" w      actionForEach =
        modelActions.createFActionForEachHomogeneous$call
        (heatbugList,
! i- P) Y7 ]) s( x         new FCallImpl (this, proto, sel,
                        new FArgumentsImpl (this, sel)));
    } catch (Exception e) {
      e.printStackTrace (System.err);
: O& K2 t4 ?/ @. t( h    }
0 V) W  c/ h* [4 Q3 E' U9 d   
    syncUpdateOrder ();
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# w" E& \6 o( G( a    try {
/ T  X" {* \5 X+ R) g      modelActions.createActionTo$message
        (heat, new Selector (heat.getClass (), "updateLattice", false));
4 R# S# W7 r8 Z3 w    } catch (Exception e) {
      System.err.println("Exception updateLattice: " + e.getMessage ());
, e8 j. f. ?+ A' `4 E    }
        
. X3 F6 H; d" Y/ Q* w    // Then we create a schedule that executes the
* V/ }4 L3 f  l) H    // modelActions. modelActions is an ActionGroup, by itself it
    // has no notion of time. In order to have it executed in
( \) C  z5 m4 ^- S# ]5 P    // time, we create a Schedule that says to use the
    // modelActions ActionGroup at particular times.  This
2 I2 l& b% }- n; U  M    // 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.
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& n# E  x; T& m9 ~    // This is a simple schedule, with only one action that is
    // just repeated every time. See jmousetrap for more
) p0 s& K' y7 {* G. y  X    // complicated schedules.
0 l  @' o! X. t8 s& o  
    modelSchedule = new ScheduleImpl (getZone (), 1);
    modelSchedule.at$createAction (0, modelActions);
        
    return this;
1 A4 k: P6 k/ p+ `% Q) K: L! R  }