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：
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" v. D3 ?  e2 ?( w3 U8 E) S public Object buildActions () {
7 h8 E0 U6 m& a! ^! q0 ?    super.buildActions();
   
; ~# B6 C! e2 U' ^; f' w    // Create the list of simulation actions. We put these in
) \+ R& Z5 h' ]6 L    // 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
    // called <foo>". You can send a message To a particular
6 f( W7 J& x" h' X% m6 ^    // object, or ForEach object in a collection.
/ c4 o$ L! Z1 x3 f. @9 G, E        
- }4 ]. z# @6 F( u  ~    // 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
0 @: q$ Q$ }8 h    // significant!
        
    // Note also, that with the additional
2 H1 G) X- x$ V2 n* y2 U0 v    // `randomizeHeatbugUpdateOrder' Boolean flag we can
/ g' H+ o3 L6 k, X    // randomize the order in which the bugs actually run
    // their step rule.  This has the effect of removing any
: ?, B' B8 z$ f3 v2 u0 p) [    // systematic bias in the iteration throught the heatbug
    // list from timestep to timestep
, T1 U; \+ V" \$ Q        
    // By default, all `createActionForEach' modelActions have
    // a default order of `Sequential', which means that the
    // order of iteration through the `heatbugList' will be
    // identical (assuming the list order is not changed
    // indirectly by some other process).
   
    modelActions = new ActionGroupImpl (getZone ());
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    try {
      modelActions.createActionTo$message
        (heat, new Selector (heat.getClass (), "stepRule", false));
    } catch (Exception e) {
      System.err.println ("Exception stepRule: " + e.getMessage ());
    }
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/ n" ]' L# [2 y' O    try {
      Heatbug proto = (Heatbug) heatbugList.get (0);
      Selector sel =
* Z' t2 F, E+ p        new Selector (proto.getClass (), "heatbugStep", false);
      actionForEach =
        modelActions.createFActionForEachHomogeneous$call
        (heatbugList,
2 P0 L- P+ E1 a$ D2 H         new FCallImpl (this, proto, sel,
                        new FArgumentsImpl (this, sel)));
    } catch (Exception e) {
9 @8 z+ D7 D! P6 Z4 @' ~      e.printStackTrace (System.err);
    }
   
, I/ v! ?( g3 s! H    syncUpdateOrder ();

    try {
      modelActions.createActionTo$message
/ G' f, d1 ~) L; y        (heat, new Selector (heat.getClass (), "updateLattice", false));
    } catch (Exception e) {
      System.err.println("Exception updateLattice: " + e.getMessage ());
2 i; {' \( P; ^    }
        
    // Then we create a schedule that executes the
    // modelActions. modelActions is an ActionGroup, by itself it
; }2 j, }9 c3 P$ c2 `' z6 S    // has no notion of time. In order to have it executed in
    // time, we create a Schedule that says to use the
+ b* P7 o+ a$ ^+ R) j, w- f4 x$ I    // modelActions ActionGroup at particular times.  This
    // schedule has a repeat interval of 1, it will loop every
6 F5 K+ R3 ]" o6 J/ X/ N    // time step.  The action is executed at time 0 relative to
2 Z  }% S5 `/ T  b  H0 Y    // the beginning of the loop.

    // This is a simple schedule, with only one action that is
2 [, a, O& [9 d4 M. `' T; ~- @    // just repeated every time. See jmousetrap for more
    // complicated schedules.
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    modelSchedule = new ScheduleImpl (getZone (), 1);
4 l1 ^' i  b8 r; O5 Z$ N3 S0 s    modelSchedule.at$createAction (0, modelActions);
        
    return this;
6 d3 D; P. Y  Y4 P. y4 i' d; o  }