CSC 211 -- ANSWERS FOR PRACTICE FINAL C

WARNING: The code in Problems 4, 5, and 6 has not been tested.
         Watch out for typos.

1. a. See notes and textbook.

   b. a == b compares addresses of String objects,
      a.equals(b) checks to see if the strings have exactly the
      same characters.

   c. public static void main(String[] args)
      {
          int i, sum = 0;
          for(i = 0; i < args.length; i++)
              sum += Integer.parseInt(args[i]);
          System.out.println("Sum is " + sum + ".");
      }

2. After swapping a[2] and a[4], the a array looks like this:

      a[0]      a[1]       a[2]      a[3]   a[4]
     --------+--------+------------+------+----------
 "grapefruit" "orange" "watermelon" "date" "lemon"

   Then this is how the variables i, j, k, and m change

        i   j    k           m   k.charAt(m)
      ----+---+------------+---+-------------
        0   2  "watermelon"  0   'w'  
        1   1  "orange"      0   'o'
        2   2  "watermelon"  4   'r'    Output:
        3   3  "date"        0   'd'    wordgame
        4   1  "orange"      4   'g'
        5   3  "date"        1   'a'
        6   4  "lemon"       2   'm'
        7   4  "lemon"       1   'e'

3.    x[0]            x[1]          x[2]
     ======           ========      ========
     a   b              a   b        refers to same
    ---+-------       ---+-----     object as x[0]
    15  "xxxdog"       27  "yyycat"
    20  "xxxdogzzz"    29  "yyycat2"
    25  "xxxdogzzzzzz"

    Output:
    25 xxxdogzzzzzz
    29 yyycat2
    25 xxxdogzzzzzz

4b.  public class Student
     {
         private String name;
         private int id;
         private int totalHours;
         private int totalGradePoints;
         
         public Student(String n, int i, int h, int g)
         {
             name = n;
             id = i;
             totalHours = h;
             totalGradePoints = g;
         }

         public String toString()
         {
             return name + " " + id + " " + totalHours + 
                           " " + totalGradePoints;
         }

         public double getGpa()
         {
             return (double) totalGradePoints / totalHours;
         }
      }

      public class Main
      {
          public static void main(String[] args)
          {
              String n;
              int i, h, g;
              BufferedReader br = new BufferedReader(
                  new FileReader("c:\\StudentInfo.txt");
              n = br.readLine();
              i = Integer.parseInt(br.readLine());
              h = Integer.parseInt(br.readLine());
              g = Integer.parseInt(br.readLine());
              Student student = new Student(n, i, h, g);
          }
      }   

5.   public static void main(String[] args)
     {
         double minVal = 2.0;  // 2.0 is a value larger than any
                               // value in the array.
         double[] a = new double[100];
         int i;

         for(i = 0; i < 100; i++)
             a[i] = Math.random();
         for(i = 0; i < 100; i++)
             minVal = Math.min(a[i], minVal);
         System.out.println("Minimum value is " + minVal + ".");         
     }

6.

public class Main
{
    public static void main()
    {
        // The initials ui mean user interface.
        UI ui = new UI();
    }
}

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
    
public class UI extends JFrame
{
    private JPanel panel;
    private JTextField field;
    private JButton button;
    
    public UI()
    {
        panel = new JPanel();
        field = new JTextField(8);
        button = new JButton("# Vowels");
        panel.add(field);
        panel.add(button);
        setContentPane(panel);
        button.addActionListener(new CD());
        setSize(100, 100);
        show();
    }    
     
    private class CD implements ActionListener
    {
        public void actionPerformed(ActionEvent e)
        {
            String word;
            char x;
            int count = 0, i;
            word = field.getText().toUpperCase();
            for(i = 0; i < word.length(); i++)
            {
                x = word.charAt(i);
                if (x == 'A' || x == 'E' || x == 'I' ||
                    x == 'O' || x == 'U')
                        count++;
            }
            field.setText(String.valueOf(count));
        }
    }
}