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：
# k7 x( e; u6 y% t
: e* [) O1 u* j8 w0 [. o7 j3 e5 D public Object buildActions () {
4 T3 ]' r' q$ x% M    super.buildActions();
  \  G: M1 e1 f" b4 C6 J   
    // Create the list of simulation actions. We put these in
3 F$ D8 l4 g4 \* ^/ `0 c    // an action group, because we want these actions to be
    // executed in a specific order, but these steps should
    // take no (simulated) time. The M(foo) means "The message
0 O3 c) V7 f$ j, I7 U0 l: Z& [9 {    // called <foo>". You can send a message To a particular
% p3 [: x. p# Y$ s+ a. g    // object, or ForEach object in a collection.
/ V6 Q, a: a# b/ s9 T        
- _, V# N9 I8 _* V    // 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!
        
% \2 A" P# t% N- C, K/ R, |. [" l! W8 G    // Note also, that with the additional
    // `randomizeHeatbugUpdateOrder' Boolean flag we can
4 o. Q5 _/ m7 }  A0 @  X, L    // randomize the order in which the bugs actually run
6 M$ N( Z1 b( Z  ]7 M    // their step rule.  This has the effect of removing any
    // systematic bias in the iteration throught the heatbug
    // list from timestep to timestep
/ G+ y  r; r( g4 X3 h        
$ X1 W* _- J" W% d6 A* }    // By default, all `createActionForEach' modelActions have
( s( T3 t6 \% T1 R& R0 t    // a default order of `Sequential', which means that the
/ h: F' L  W1 S6 F, ^    // order of iteration through the `heatbugList' will be
    // identical (assuming the list order is not changed
    // indirectly by some other process).
  ]) {4 G/ e9 f, c# {   
1 R8 T8 ^& B4 |" h    modelActions = new ActionGroupImpl (getZone ());

    try {
" t7 A3 {& p8 V" ?9 m. o  B      modelActions.createActionTo$message
# N# W, t& S0 h7 {( k" I        (heat, new Selector (heat.getClass (), "stepRule", false));
9 W8 p+ k7 I5 o    } catch (Exception e) {
      System.err.println ("Exception stepRule: " + e.getMessage ());
    }

    try {
      Heatbug proto = (Heatbug) heatbugList.get (0);
  Q+ @+ G% Y% [) j7 \2 n  ]" W      Selector sel =
( [/ G9 @/ O; Z7 U8 [! \+ T7 x* W6 j        new Selector (proto.getClass (), "heatbugStep", false);
. T$ K7 e- t% O' }& q      actionForEach =
, x- z0 y' d5 F  J6 [" S        modelActions.createFActionForEachHomogeneous$call
        (heatbugList,
         new FCallImpl (this, proto, sel,
                        new FArgumentsImpl (this, sel)));
! M) D5 U' U5 W8 `0 K    } catch (Exception e) {
3 _1 n$ h. |+ V, v# p. n7 f4 S. s      e.printStackTrace (System.err);
$ o7 M/ ~# V4 Q& q$ e1 o    }
4 s* `2 Y2 e& h$ }. a   
    syncUpdateOrder ();

    try {
" j0 i$ o6 t0 x4 k( K6 L      modelActions.createActionTo$message
        (heat, new Selector (heat.getClass (), "updateLattice", false));
    } catch (Exception e) {
      System.err.println("Exception updateLattice: " + e.getMessage ());
. M3 T+ R0 D/ b) |. I  B4 x    }
+ Y0 M) N- C( N  j+ g  \        
9 ^4 G* `. `: m5 r% e    // 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
    // time, we create a Schedule that says to use the
5 L7 z# a6 q6 [) |) m% d& t    // modelActions ActionGroup at particular times.  This
    // schedule has a repeat interval of 1, it will loop every
7 N" s/ g. a% `- M6 I* ~8 I    // 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
    // just repeated every time. See jmousetrap for more
    // complicated schedules.
  
+ k+ K$ ?, d& ?9 ~1 t# V! s    modelSchedule = new ScheduleImpl (getZone (), 1);
; |6 C- s- Z4 ]# w) T% c    modelSchedule.at$createAction (0, modelActions);
% g0 m7 W1 R& D1 q& n/ D7 S        
' Y' C* q( C& ?3 O% Y" f  i1 v    return this;
  }