Question

1. Here is a bit of Java code:

   Thing t = new Thing();
   t.method( (int i)-> i + 1 );
   

   Here is a skeleton for class Thing:

   class Thing {
       public interface Mystery {
           ?????
       }
       public void method( Mystery param ) {
           // body of method omitted
       }
   }
   

   Which text below would work where ????? is given above:
   a) void method( int i );
   b) int method( int i );
   c) abstract int method( int i );
   d) abstract void method( int i );
   e) private int method( int i );

2. Consider the final simulation framework given at the end of the notes for Oct. 13. Suppose the following code is used in the initialization:

   Simulator.schedule( 8.0*hour, (double t)->w.open(t) );
   

   Assume that w is a workplace, and every workplace has a method open(double t) that simulates the workplace opening for business at time t.

   The value 8.0*hour is passed as t to w.open(t) through the following steps that are not given in order (and some steps are omitted):
   v) e is removed from eventSet.
   w) 8.0*hour is put in e.time for some Event e.
   x) w.open(t) is called.
   y) e.act.trigger(e.time) is called.
   z) e drifts to the head of eventSet.

   What is the correct order for these steps?
   a) vwyzx
   b) xwyvz
   c) ywzvx
   d) wzvyx
   e) zywvx

3. Assume that time zero is midnight on day zero of the simulation, so 8*hour is 8AM on day zero. Given that w is a workplace with methods open(t) and close(t), and given that the work day is 8 hours long, a workplace that opens at 8AM should close at 5PM. This requires the following code:

   public void open(double time) {
       Simulator.schedule( time + 8*hour, ------- );
   }
   

   What code belongs where the above shows -------?
   a) ()-> open( time )
   b) (double t)-> open( t )
   c) this.open( time )
   d) ()-> this.open( time );
   e) (double t)-> this.open( t )
4. Given that we are using type double to represent time, we could define day = 1.0 so that hours are fractional days. If we do this, we should define hour as:
   a) final double hour = 0.4166;
   b) double hour = 1 / 24;
   d) final double hour = day * 0.4166;
   c) double hour = day * 0.4166;
   e) final double hour = day / 24.0;
5. Suppose we want to model weekends? To do this, when a workplace closes at 5PM on a normal weekday, it schedules itself to reopen 16 hours later at 8AM, but on Friday afternoon, it should schedule itself to open 54 hours later, that is, skipping an extra 48 hours. Assume that day zero begins at the midnight separating Sunday from Monday. What expression below is true only on Friday?
   
   a) (Double.intValue( time ) % 7) == 4
   b) ( time % 7) == 4
   c) (Double.intValue( time ) % 7) == 5
   d) ( time % 7) == 5
   e) (Double.intValue( time ) / 7) == 0.5

Answer 1