ANSWERS TO MIDTERM D

1.a. See Lecture Summary from 6/24/02.

1.b. Although writing your own classes is rather complex,
     using classes is fairly straightforward for beginning
     programmers.  Most Java textbooks take the "objects
     early" approach, where objects are used from Day 1,
     but writing classes is postponed until later (until
     after the midterm in our case.)

     Here are some of the classes that we have used before 
     the midterm:  System, Coin, String, DecimalFormat, Math, 
     Applet, Color, Graphics.  There is also the NumberFormat
     class discussed in the text that is useful, but which we
     didn't discuss.

2.     x     y     z      a         x > 0 && y > 0    x >= y
     -----+-----+-----+----------+------------------+----------
      60    100    0                     true          false
      20     25    1   1-1               true          false
       6      6    2   2-1-12            true          true
       2      1    3   3-2-1-123         true          true
       0      0    4   4-3-2-1-1234      false

     Output:
     60100
     251-120
     62-1-126
     23-2-1-1231

3. public static void main(String args[])
   {
       String inputString, outputString;
       int len;

       inputString = JOptionPane.showInputDialog("Enter a string")); 
       len = inputString.length();
       if (inputString.charAt(0) == 'e' ||
               inputString.charAt(len - 1))
           outputString = "Yes";
       else
           outputString = "No";
       System.out.println(outputString);
   }

4. public static void main(String args[])
   {
       double hoursWorked, overtimeHours = 0.0;
       int overtimeCount = 0;

       hoursWorked = Double.parseDouble(
            JOptionPane.showInputDialog("Enter hours worked."));
       while(hoursWorked >= 0)
       {
           if (hoursWorked > 40)
           {
               overtimeHours += hoursWorked - 40;
               overtimeCount++;
           }
           hoursWorked = Double.parseDouble(
               JOptionPane.showInputDialog("Enter hours worked."));
       }
       System.out.println(
           "Total overtime hours are " + overtimeHours);
       System.out.println(
           "Numbers of employees with overtime are " + 
           overtimeCount);
   }

5.  public class MyApplet extends Applet
    {
        public void init()
        {
	    setBackground(Color.white);
            setSize(150, 150);
        }

        public void paint(Graphics g)
        {
            for(int x = 0; x <= 150; x += 10)
                g.drawLine(0, 0, x, 150);
        }
    }