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581258-1 Introduction to Programming: 2. exam 18.12.1997/AW

Please write on the top of each of your papers the name of the course, the date of the exam, your name, your date of birth and your signature.

You may use the tools of the Lue-class when writing your programs.

1. Compare the following concepts concisely and precisely:

   primitive type - reference type
   compilation unit - package
   instantiation (creating an object) - class loading
                                                              (6 points)

2. • a) Program a method sort for sorting an array of integers to ascending order. The array is passed as a parameter to the method.
   • b) Make a method BinSearch that will search for an integer in an array. The array and the integer are passed as a parameters to the method. If the integer is found, the method returns the inxed of the integer in the array. If the value is not found, -1 is returned.
   • c) Write - by using the methods of a)- ja b) - a program that will first read a set of integers provided by the user. Then the numbers are sorted. After this the user can search values from the array. Design how to quit the use of the program. The program must give the user clear instructions.

                                                         (5 points)

3. Class Example is defined as follows:

  public class Example {
    public int[] iT;
    static private double d;
    public Example() {
      iT = new int[10]; d = 3.14;
    }
    void metA() {
      System.out.println(iT.length);
    }
    public int metB(int par) {
      return iT.length+par;
    }
    static String metC(char c) {
      return ""+d+c;
    }
  }

Write a subclass Sub for the class Example. Sub must hide the field d, override the method metC, inherit the method metB and overload the method metA.What is the easiest way to use the hidden, overridden, inherited, and overloaded parts in class Sub? Or is it possible to use them?

                                                              (5 points)

4. Explain the scope rules of Java. What scope areas there are, and how the visibility (usability) of names (identifiers) is controlled? When a name "Name" is used inside a method, from where and in what order the meaning of the name is searched?

                                                              (5 points)

5. You are given a class called InpFile for reading an input file. The class has a constructor:

• InpFile(String name) that creates an InpFile object with which you can read a text file. The name of the file is passed as a parameter. If the file is not found, the read-method will return null values right from the start. So, empty and missing files will behave similarly to the user of this class! The user doesn't have to take care for any exceptions.

The class contains a method for reading lines:

• String read() returns next line from the input file. When the file ends (or doesn't exist at all!) the method will return the value null.

By using this class, write a program that asks the user for the name of the input file, a character to be replaced (oldChar), and a replacing character (newChar). Then the program prints the file, modified so that all oldChar-characters are replaced by the newChar-character.

                                                              (5 points)