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 y5 ^2 D$ ?* j
public Object buildActions () {
: C2 Q* w# C6 j* F# Q$ _9 ]8 l! U    super.buildActions();
   
    // Create the list of simulation actions. We put these in
: I# K) \) |) M6 u- }7 T6 P( e    // an action group, because we want these actions to be
    // executed in a specific order, but these steps should
" n# A- _2 S7 f7 Q$ `2 b    // take no (simulated) time. The M(foo) means "The message
    // called <foo>". You can send a message To a particular
, w. r& H+ }$ K) l2 x- J    // object, or ForEach object in a collection.
        
    // Note we update the heatspace in two phases: first run
. H+ u  |3 {! a" T  }- s5 n: z$ Z    // diffusion, then run "updateWorld" to actually enact the
    // changes the heatbugs have made. The ordering here is
    // significant!
        
7 \8 P1 J- x/ d: |, B. p    // Note also, that with the additional
8 J9 W  ]& P2 l0 |    // `randomizeHeatbugUpdateOrder' Boolean flag we can
    // randomize the order in which the bugs actually run
; a, A* g4 E8 h6 X    // their step rule.  This has the effect of removing any
    // systematic bias in the iteration throught the heatbug
# V/ M; Y- Q! C3 n# r/ B    // list from timestep to timestep
        
    // By default, all `createActionForEach' modelActions have
    // a default order of `Sequential', which means that the
* D1 R4 u9 P8 L* r9 Q# ?    // order of iteration through the `heatbugList' will be
    // identical (assuming the list order is not changed
, M, @, t+ y( J) S# O    // indirectly by some other process).
! {4 }) S' G" j5 [( A7 k* x   
    modelActions = new ActionGroupImpl (getZone ());

    try {
      modelActions.createActionTo$message
4 {: x3 K2 K  |2 J* @        (heat, new Selector (heat.getClass (), "stepRule", false));
    } catch (Exception e) {
: I7 B. f: u+ A8 R( T7 i      System.err.println ("Exception stepRule: " + e.getMessage ());
    }

    try {
, a% m0 @/ d5 p) \/ {      Heatbug proto = (Heatbug) heatbugList.get (0);
      Selector sel =
        new Selector (proto.getClass (), "heatbugStep", false);
      actionForEach =
        modelActions.createFActionForEachHomogeneous$call
6 ?( P4 I; B$ G- I* v        (heatbugList,
         new FCallImpl (this, proto, sel,
                        new FArgumentsImpl (this, sel)));
    } catch (Exception e) {
      e.printStackTrace (System.err);
    }
   
. @! e( U" C$ c1 `    syncUpdateOrder ();
) A! g, y7 z; Y# y3 b7 a
  X& w; f4 k- b& _+ s4 c/ |    try {
      modelActions.createActionTo$message
6 }/ e& f" `0 e7 A        (heat, new Selector (heat.getClass (), "updateLattice", false));
    } catch (Exception e) {
! [4 C+ s3 p. V3 J4 J) f) ^0 w      System.err.println("Exception updateLattice: " + e.getMessage ());
! A% y1 o9 `3 n3 a' M* ~    }
! ^0 F3 l% _+ ?+ V- c% o, a! j7 l        
    // Then we create a schedule that executes the
, E/ U! n* i1 E, u# i! o( g+ R    // modelActions. modelActions is an ActionGroup, by itself it
5 t3 X) S! }7 }- h) k5 R7 i. P; X    // has no notion of time. In order to have it executed in
; ~$ G7 ?4 r9 {6 z  `; u    // time, we create a Schedule that says to use the
    // 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
; y5 \5 o2 S& o, m    // the beginning of the loop.

, @+ E  Q+ s, Z1 k9 Z: ~- Q    // This is a simple schedule, with only one action that is
    // just repeated every time. See jmousetrap for more
    // complicated schedules.
9 P/ F$ N% D% v* y& X$ H  
- q/ B/ H- q# K2 C4 P4 H; }1 n    modelSchedule = new ScheduleImpl (getZone (), 1);
    modelSchedule.at$createAction (0, modelActions);
        
, Z2 v6 ^6 F$ z3 O7 R- y    return this;
  }