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 }# }, A, a$ q
public Object buildActions () {
    super.buildActions();
   
    // Create the list of simulation actions. We put these in
; ^. X1 ?$ Q' ~, q& \6 T, a1 [. V    // an action group, because we want these actions to be
    // executed in a specific order, but these steps should
/ T5 f5 K/ z3 r- P, L7 T  c    // take no (simulated) time. The M(foo) means "The message
! \1 D7 F+ |+ }" C* i    // 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
1 e1 I$ j' L# |! S  Q3 j; ?' V( C    // diffusion, then run "updateWorld" to actually enact the
    // changes the heatbugs have made. The ordering here is
    // significant!
* Q2 M- d) i3 V2 [+ G, U; E        
    // 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
  X- A: z% w( y* u& U' o2 m    // systematic bias in the iteration throught the heatbug
    // list from timestep to timestep
4 q' r, Z% M# R9 _/ G0 e        
    // By default, all `createActionForEach' modelActions have
    // a default order of `Sequential', which means that the
$ F" ?+ m( J2 i2 C0 [    // order of iteration through the `heatbugList' will be
    // identical (assuming the list order is not changed
    // indirectly by some other process).
" Y3 Q2 L$ H" K+ m   
    modelActions = new ActionGroupImpl (getZone ());
* p1 M+ b- u% l, r3 r
- @- g; l* {- e3 m9 j, [    try {
      modelActions.createActionTo$message
        (heat, new Selector (heat.getClass (), "stepRule", false));
: z* p& i: \6 }; p( k    } catch (Exception e) {
      System.err.println ("Exception stepRule: " + e.getMessage ());
    }

* ~* S$ q0 {4 d& W2 k  M: s* n! l    try {
; H& m; e& ]7 C      Heatbug proto = (Heatbug) heatbugList.get (0);
      Selector sel =
" {- ~4 R2 Y* h4 h        new Selector (proto.getClass (), "heatbugStep", false);
      actionForEach =
        modelActions.createFActionForEachHomogeneous$call
6 g' e! b* f/ E- w' {        (heatbugList,
         new FCallImpl (this, proto, sel,
9 T: q/ I" J. Z                        new FArgumentsImpl (this, sel)));
8 @- H0 C: u" ~. T! U! h    } catch (Exception e) {
      e.printStackTrace (System.err);
    }
" e2 H/ @3 E2 u  t   
; ]) y: r. X6 `8 e' m6 K    syncUpdateOrder ();

    try {
' w4 m, Z. r& S      modelActions.createActionTo$message
        (heat, new Selector (heat.getClass (), "updateLattice", false));
! z3 z1 U4 z* b: v  b5 j    } catch (Exception e) {
( ]5 L  d5 t: t' C9 V      System.err.println("Exception updateLattice: " + e.getMessage ());
    }
) z' ~0 @4 L! C        
    // Then we create a schedule that executes the
    // modelActions. modelActions is an ActionGroup, by itself it
    // has no notion of time. In order to have it executed in
' P: J. p) g$ i; J# d3 o    // time, we create a Schedule that says to use the
    // modelActions ActionGroup at particular times.  This
& Y8 C- [& J4 s+ y! C- C3 t    // 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.

    // This is a simple schedule, with only one action that is
: {1 Z0 i, E7 k$ Q: ~2 U    // just repeated every time. See jmousetrap for more
+ q4 E- D" _$ o    // complicated schedules.
  
    modelSchedule = new ScheduleImpl (getZone (), 1);
    modelSchedule.at$createAction (0, modelActions);
        
% R; G9 Z4 }( R, q  E4 ^9 b* M$ N    return this;
  }