581325-0 Introduction to Programming, course examination 14.11.2003/AW

Write the name of the course, the date of the exam, your name, personal
number and signature on each paper. 

1. "What in the world is encapsulation?" your friend asks after
   listening to your stories about the course Introduction to
   Programming. Your friend has done a little programming, enough to
   know variables, expressions, statements and methods. He has even
   managed to program some primitive classes for creating objects.
   "But what do you 'encapsulate' and what ever for?", he asks
   you. Help your friend understand what it is all about. Write an
   explanation (a maximum of one sheet). Please keep in mind that
   examples are a great aid to learning. When evaluating the answer,
   we will take into account the intended reader, so do not write for
   the evaluator, who already knows the subject, but for that friend
   of yours!
                                                               (16 points)

2.  There are two fuel tanks at the gas station. You can only add gas
    directly to the main tank, and clients can only take out gas from
    the main tank. The second tank is a reserve tank, which is used
    automatically when the capacity of the first tank runs out. Write
    the class GasStation to implement the gas station.

    - public GasStation (double mainTank, double reserveTank) creates
      the gas station, the parameters given are the capacities of the
      tanks. If there is an error in the capacity, the capacity of the
      tank is set to 5000 litres. Both tanks are empty to begin with.

    - public double main tankContains() returns the amount of gas in
      the main tank
    - public double reserveContains() returns the amount of gas in the
      reserve tank
    - public double totalGas() returns the total amount of gas in the
      gas station

    - public boolean addGas(double amount) adds gas to the main tank.
      If you try to add more than the tank's capacity, the excess gas
      is pumped into the reserve tank. If the total amount added is more
      than the total capacity of the tanks, the amount of gas does not
      change in either tank. The method returns true if the gas is
      added, false if it is not.

    - public double fillupGas(double amount) takes gas out of the main
      tank. If the request is for more than there is in the main tank,
      gas can be transferred automatically from the reserve tank to the
      main one. If the total amount of gas is less than was requested,
      as much is given as there is left. The method returns the amount
      of gas given.

    - public String toString() returns a clear character string
      presentation of the gas station's status.
                                                               (18 points)

3. Implement the following guessing game as an interactive program. 
   Before the game starts the game leader inputs 100 integers into the
   program in random order.  Then the player starts to use the program. The
   player tries to guess the numebers that the game leader has input in the
   computer. The game ends, when the player has guessed three different
   numbers. The result is the number of guesses, so it is at least three.

   You may assume that the game leader really inputs 100 different numbers.
   For the sake of efficiency, the search for guessed numbers must be
   programmed with the Binary Search
                                                               (16 points)
                         Sunny and Warm Summer!