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：
7 z# ?: U, ]% u5 f( g
6 c7 F; ?' l. O5 T9 I2 L) ~# X public Object buildActions () {
    super.buildActions();
) u$ ]2 _$ v8 {$ I$ W: a1 G; w9 h   
    // Create the list of simulation actions. We put these in
    // an action group, because we want these actions to be
% [8 ^, _/ j( @3 ~% ], [    // executed in a specific order, but these steps should
    // take no (simulated) time. The M(foo) means "The message
5 M$ h+ U0 W$ Z    // called <foo>". You can send a message To a particular
6 g# j3 z* G" b  \$ N% Q6 \+ `  Z/ e    // object, or ForEach object in a collection.
0 I) r' O) o' _" x        
    // Note we update the heatspace in two phases: first run
; x" k' I3 P, s' g1 f$ O    // diffusion, then run "updateWorld" to actually enact the
6 D& `9 K+ S/ T! D& }    // changes the heatbugs have made. The ordering here is
) M3 Y0 O) l) t- u# G    // significant!
( D/ _( v/ J2 J& D, d        
: ?" i2 W& ^1 I* K) ?; Z7 G- V    // Note also, that with the additional
    // `randomizeHeatbugUpdateOrder' Boolean flag we can
    // randomize the order in which the bugs actually run
: E0 ~8 ~4 F- n3 e" F8 R    // their step rule.  This has the effect of removing any
    // systematic bias in the iteration throught the heatbug
. S% f8 G# ]& Q3 M+ s' V/ \7 }    // list from timestep to timestep
' s6 D* Z5 `6 V$ T$ l5 w$ h% |# z        
    // By default, all `createActionForEach' modelActions have
    // a default order of `Sequential', which means that the
0 y7 `3 ~% x" @6 q5 ~    // order of iteration through the `heatbugList' will be
    // identical (assuming the list order is not changed
    // indirectly by some other process).
   
$ \* K/ ~7 m* c2 ?" x0 w1 [    modelActions = new ActionGroupImpl (getZone ());
; I4 k# N: x; r
    try {
! q! F# b) Y5 d# o      modelActions.createActionTo$message
        (heat, new Selector (heat.getClass (), "stepRule", false));
    } catch (Exception e) {
! t; C2 g: h, n' x5 R      System.err.println ("Exception stepRule: " + e.getMessage ());
% [+ J  e  M9 V1 B# J+ {9 ]    }
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    try {
, K" g6 h& n- ~# r" [      Heatbug proto = (Heatbug) heatbugList.get (0);
      Selector sel =
* o" P( W" Q' V        new Selector (proto.getClass (), "heatbugStep", false);
      actionForEach =
        modelActions.createFActionForEachHomogeneous$call
        (heatbugList,
         new FCallImpl (this, proto, sel,
% \, b& Y( h% t0 r. t                        new FArgumentsImpl (this, sel)));
6 Z1 N) E6 ~7 }% J8 C- s    } catch (Exception e) {
" i* X4 k% }  x6 v1 M      e.printStackTrace (System.err);
    }
   
- w) u. S+ U8 h    syncUpdateOrder ();

    try {
5 n: ^" G  b" U* v% r      modelActions.createActionTo$message
5 e* X- t, s  f        (heat, new Selector (heat.getClass (), "updateLattice", false));
    } catch (Exception e) {
      System.err.println("Exception updateLattice: " + e.getMessage ());
1 v  {1 j, `& Z! [    }
        
    // Then we create a schedule that executes the
  y* G7 }2 s' ~: |    // modelActions. modelActions is an ActionGroup, by itself it
    // has no notion of time. In order to have it executed in
7 z& _) |1 v" _    // time, we create a Schedule that says to use the
    // modelActions ActionGroup at particular times.  This
% k9 o6 K/ g5 e    // schedule has a repeat interval of 1, it will loop every
0 F1 ]! Z. {- V( y+ H* ?# l: E+ C    // time step.  The action is executed at time 0 relative to
& Q" ]# F% t# O    // the beginning of the loop.
- R$ |  O0 C, W' }* H' b
    // This is a simple schedule, with only one action that is
    // just repeated every time. See jmousetrap for more
$ O; r+ m" I- t! j: `: Y4 i    // complicated schedules.
' x/ v( |+ V7 }5 t  
    modelSchedule = new ScheduleImpl (getZone (), 1);
    modelSchedule.at$createAction (0, modelActions);
! H/ W, |3 H6 I- ?& T# }        
    return this;
/ ]5 Q- r0 P# a5 @  }