In-Class Examination 1

• Before you answer any questions, write your name and perm number.
• Read each question carefully.  Make sure that you clearly understand each question before answering it.
• Put your answer to each question on its own page.
• You may wish to work out an answer on scratch paper before writing it on your answer page; answers that are difficult to read may lose points for that reason.
• Each question is worth 20 points.

        // some Java statements are omitted that assign values to i, j, k, & l.

        // Your Java statement goes here

Create a single Java statement that assigns new values to i, j, k, and m as follows (in the order indicated):

1. Increment i's value by 1
2. Multiplies  j by the sum of i's new value and m's current value
3. Assigns to k the remainder of its current value when divided by j's new value
4. Decrements m by 1.

Solution:

---

        // some Java statements are omitted that assign value to i, j, k, & m.

        k %= j *= ++i + m--;

---


Solution:

In the picture above, painting is inset 40 pixels from the left and the top.  Each black square has an edge length of edg; there are num such squares on the diagonal and anti-diagonal.

---


import java.awt.*;
import java.applet.*;
import java.awt.event.*;

public class test1 extends Applet
                   implements ActionListener, MouseListener
{
    int num = 5, edg = 20, x, y;
    boolean clicked = false;
    Label     numL  = new Label("Number:"),
              edgL  = new Label("Edge length:");
    TextField numT  = new TextField("5", 2),
              edgT  = new TextField("20", 2);

    public void init() {
        add(numL); add(numT);
        add(edgL); add(edgT);
        numT.addActionListener(this);
        edgT.addActionListener(this);
        addMouseListener(this);
    }
    public void paint(Graphics g)
    {
       // Your code to paint the red and black squares goes here
 

       // Your code to process the mouse release goes here (see Question 4)
    }

    public void actionPerformed(ActionEvent e) {
        num = Integer.parseInt(numT.getText());
        edg = Integer.parseInt(edgT.getText());
        repaint();
    }
    public void mousePressed(MouseEvent e) {}
    public void mouseClicked(MouseEvent e)  {}
    public void mouseReleased(MouseEvent e) {
        x = e.getX();
        y = e.getY();
        clicked = true;
        repaint();
        }
    public void mouseEntered(MouseEvent e)  {}
    public void mouseExited(MouseEvent e)   {}
}


---


Solution:

---


    public void paint(Graphics g)
    {
        g.setColor(Color.red);
        g.fillRect(40, 40, num*edg, num*edg);
        g.setColor(Color.black);
        for (int i = 0; i < num; i++)
        {
            g.fillRect(40 + edg*i, 40 + edg*i, edg, edg);
            g.fillRect(40 + edg*i, 40 + (num - 1 - i)*edg, edg, edg);
        }
    }


---

Solution:

---


        int col = (x - 40)/edg;
        int row = (y - 40)/edg;
        g.setColor(Color.blue);
        if ( clicked &&                     // mouse was clicked
             40 < x && x < 40 * num*edg &&  // x coordinate in box
             40 < y && y < 40 + num*edg &&  // y coordinate in box
             (row == col || num - 1 - row == col) // in black square
           )
                    g.fillRect(40 + col*edg, 40 + row*edg, edg, edg);


---

Solution:

---