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：
2 ~* R% P0 G1 ?/ V- ]% ~
3 l" ?0 q3 z# a! d# m2 l public Object buildActions () {
    super.buildActions();
   
7 V; b% _+ i1 U* b( ~5 n& }    // Create the list of simulation actions. We put these in
: O) n% D, A$ Z6 H5 Q    // an action group, because we want these actions to be
5 L, C2 M4 z5 p1 I0 w, t    // executed in a specific order, but these steps should
7 p" m) b" k3 v4 _    // 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.
        
    // 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!
" f9 L( R% J* |6 `        
1 e0 {5 [3 }9 c    // Note also, that with the additional
    // `randomizeHeatbugUpdateOrder' Boolean flag we can
    // 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
7 [! s3 y0 I& Q  X+ D. R+ @        
/ m9 U3 D1 h- e5 V$ u6 i    // By default, all `createActionForEach' modelActions have
    // a default order of `Sequential', which means that the
# S2 F: f& L7 X" o5 Z+ k7 r( a    // order of iteration through the `heatbugList' will be
    // identical (assuming the list order is not changed
    // indirectly by some other process).
) J6 R& I' U7 W8 O0 B/ Y   
# Q- s5 n& ]+ N: i    modelActions = new ActionGroupImpl (getZone ());
/ H& T. x8 e$ I5 t* H! h/ R) C
    try {
      modelActions.createActionTo$message
        (heat, new Selector (heat.getClass (), "stepRule", false));
% i0 p1 ]' a, i    } catch (Exception e) {
      System.err.println ("Exception stepRule: " + e.getMessage ());
    }

    try {
$ A% |5 r2 ~# j8 ^      Heatbug proto = (Heatbug) heatbugList.get (0);
' \# \. h: o. Z- y) L* b      Selector sel =
% g5 W) H  G. B- t        new Selector (proto.getClass (), "heatbugStep", false);
      actionForEach =
8 b6 X0 E( s( w* r3 O6 s8 L        modelActions.createFActionForEachHomogeneous$call
1 q& A  I1 T& n2 @/ U7 A" w        (heatbugList,
$ d) h5 l1 R& Z; c( u         new FCallImpl (this, proto, sel,
- l, @' J  l( n  O5 r. I  g( q                        new FArgumentsImpl (this, sel)));
    } catch (Exception e) {
* e+ _/ A) e1 S& I0 g4 E0 @& g      e.printStackTrace (System.err);
    }
   
9 h) r& H  V5 L' ]6 k    syncUpdateOrder ();

    try {
# h8 h8 A' H# n) X+ x      modelActions.createActionTo$message
        (heat, new Selector (heat.getClass (), "updateLattice", false));
    } catch (Exception e) {
- M# m6 R1 w& s& M" n% j      System.err.println("Exception updateLattice: " + e.getMessage ());
    }
) k* K9 w% U8 k; f) c( y( C        
7 S+ Y! o$ b( T0 Y/ g: A! D; Y    // Then we create a schedule that executes the
  i/ N' Z9 y; k  }0 N8 S    // modelActions. modelActions is an ActionGroup, by itself it
    // has no notion of time. In order to have it executed in
( h5 ~' c5 _  N  }* W2 S! S    // time, we create a Schedule that says to use the
    // modelActions ActionGroup at particular times.  This
% @' R$ x6 t6 C) o% y# \    // schedule has a repeat interval of 1, it will loop every
    // time step.  The action is executed at time 0 relative to
: o% _1 b  k7 y% V& m) d    // the beginning of the loop.

    // This is a simple schedule, with only one action that is
    // just repeated every time. See jmousetrap for more
3 S* ?2 ^# ~/ @# X+ c    // complicated schedules.
  
    modelSchedule = new ScheduleImpl (getZone (), 1);
. Z9 l; E4 j% w3 F; X& e    modelSchedule.at$createAction (0, modelActions);
        
5 F) e# o4 ]4 H( z( x; c, _    return this;
  }