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Fish Location Analysis in Bounded Environment

Study on how Fish class interacts with its environment, checking inconsistencies and methods for state manipulation.

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Fish Location Analysis in Bounded Environment

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  1. MBCS Chapter2 Analysis Question sets 4-6

  2. Fish Notice the line Implements Locatable In the definition for Fish class

  3. Fish accessor methods • Id • Environment • Color • Location • Direction • isInEnv • toString

  4. isInEnv • Tests • Is the fish in this environment? • At the expected location? • Compares what the fish thinks to what the environment thinks • If not = inconsistent

  5. Public boolean isInEnv() { return (environment().objectAt(location()) == this); } this = the current object Meaning = is this fish recognized by the environment to be at the location where it thinks it is?

  6. The Bounded Environment • Which methods could possibly create an inconsistent state? • numRows() • numCOls() • isValid(Location loc) • numObjects() • allObjects() • isEmpty() Think about it! …. But wait, there are more…..

  7. Which methods could possibly create an inconsistent state? • objectAt(Location loc) • toString() • Add(Locatable obj) • Remove(Locatable obj) • recordMove(Locatable obj, Location, oldLoc)

  8. Answers to set 4

  9. Set 4 • Look at Fish initialize method. • Last step = add fish to theEnv • Environment receives fish, including location • Adds only if location not full • Fish & environment are in agreement • If a fish is removed from it’s environment (eaten or dies) it still “thinks” it’s at a certain location, but it’s not. • = inconsistent state

  10. Why? • Why does act check to see if the fish is still in the environment and the call move? • Why not get rid of act and just use move? • Eventually fish breed, die, etc… they do much more than just move. • Makes it easy to override specific methods of behavior, not just moving.

  11. Answers to set 5

  12. Set 5 • True, true • False, false • False, true

  13. Answers to set 6

  14. Set 6 • neighborsOf returns all valid neighboring locations • Not just empty • emptyNeighbors code could have been included in nextLocation • BUT GOOD OOP = each method does 1 well-defined task • Putting emptyNeighbors in nextLoaction would have made it overly complicated.

  15. Do Exercise 3 • Import java.util.ArrayList; • Public class Ch2Ex3 • { • Construct an environment and some fish • To get answers: • Create 3 locations • Create 3 arraylists of the neighbors of the locations • Display number of neighbors and locations using loops. • } // it should be easy to figure out which other locations have the same number of neighbors.

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