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：
0 \2 Z( F8 j# `8 ^' J$ J
public Object buildActions () {
. V8 J$ z* ~/ _- Q! E    super.buildActions();
. u! W( j% N/ z0 p/ ?$ F   
( C1 }2 ^- r0 ^) U0 p    // Create the list of simulation actions. We put these in
8 u0 b# w3 t7 P2 E2 F$ Y4 t) j: ?    // an action group, because we want these actions to be
+ }" ~6 v/ A3 [9 i: O( N    // 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
2 S& `# L  K' {$ `    // object, or ForEach object in a collection.
        
8 o+ P; I( t; b/ R8 G/ I# T. S' t    // Note we update the heatspace in two phases: first run
    // diffusion, then run "updateWorld" to actually enact the
+ D0 N- F# K* v1 ?    // changes the heatbugs have made. The ordering here is
    // significant!
5 |0 H/ `& ?/ V8 B/ l0 e5 a& v        
    // Note also, that with the additional
3 A: b  z% J% P# G* }    // `randomizeHeatbugUpdateOrder' Boolean flag we can
7 Z7 }( T5 l+ i    // 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
" e/ J8 n# t& j' e" m2 ?) w        
7 A  D, S" t! ?) x  _9 d    // 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).
+ P% d- v" a0 V   
    modelActions = new ActionGroupImpl (getZone ());
2 d* V2 d+ V9 D* c& t! W; D
& r, Y4 F4 A, |- _1 f/ j+ I9 ?) t7 t    try {
2 g- G* |, E0 h% t$ I( P      modelActions.createActionTo$message
        (heat, new Selector (heat.getClass (), "stepRule", false));
    } catch (Exception e) {
      System.err.println ("Exception stepRule: " + e.getMessage ());
    }
5 u7 g3 ]( q& ^* X" E" }
! ?2 ~6 N* a, e' E& U% p    try {
- G1 X- g; T! c" A( m- R( w+ S      Heatbug proto = (Heatbug) heatbugList.get (0);
6 n8 I, ?! Q. a      Selector sel =
& c2 X& ^) s) H        new Selector (proto.getClass (), "heatbugStep", false);
5 |3 B+ ~$ `, ?) Q) V      actionForEach =
        modelActions.createFActionForEachHomogeneous$call
+ |$ Q) h+ H$ r. t+ J$ O, |  z1 w        (heatbugList,
         new FCallImpl (this, proto, sel,
                        new FArgumentsImpl (this, sel)));
0 R: G) O; X, |) W    } catch (Exception e) {
1 f0 r5 J6 y3 |& R      e.printStackTrace (System.err);
4 k& o: a0 T3 m; |1 ~4 k    }
   
    syncUpdateOrder ();

    try {
9 a4 X& I- R7 l' j      modelActions.createActionTo$message
        (heat, new Selector (heat.getClass (), "updateLattice", false));
2 J; m% e! t- G" z. c    } catch (Exception e) {
      System.err.println("Exception updateLattice: " + e.getMessage ());
    }
        
' m$ C$ D$ x! ~    // Then we create a schedule that executes the
    // modelActions. modelActions is an ActionGroup, by itself it
- b9 O+ _; H  K) d; V. z    // has no notion of time. In order to have it executed in
    // time, we create a Schedule that says to use the
% M0 \' j8 ]7 j* C7 s    // 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
: U- f3 f# v) q$ H1 g2 |    // the beginning of the loop.
) f+ V6 K) |4 C! J5 \
    // This is a simple schedule, with only one action that is
    // just repeated every time. See jmousetrap for more
    // complicated schedules.
: i7 y5 _* q+ _' m+ A  
! l: U* z+ D, i, V5 X. s; ^    modelSchedule = new ScheduleImpl (getZone (), 1);
    modelSchedule.at$createAction (0, modelActions);
+ ~6 h/ {7 o0 B3 Y! H: E        
: N" {9 W( e+ q" b  C! T' A    return this;
" i0 H. |8 l4 M7 v9 Q+ y. B  }