<![CDATA[
Key to CSE190L Sample Midterm handout #16
Spring 2007
1. Statement Output
--------------------------------------------------
var1.method1(); Water 1/Tea 2/Water 2
var2.method1(); Water 1/Milk 2
var3.method1(); Water 1/Water 2
var4.method1(); Water 1/Milk 2
var5.method1(); compiler error
var1.method2(); Tea 2/Water 2
var2.method2(); Milk 2
var3.method2(); Water 2
var4.method2(); Milk 2
var1.method3(); compiler error
var2.method3(); Milk 3
var3.method3(); compiler error
((Water)var5).method1(); Water 1/Water 2
((Cola)var3).method3(); Cola 3
((Water)var5).method2(); Water 2
((Milk)var6).method2(); runtime error
((Tea)var4).method3(); Milk 3
((Tea)var3).method3(); runtime error
((Tea)var1).method3(); Tea 3
((Water)var6).method3(); compiler error
2. One possible solution appears below.
public class RectanglePanel extends JPanel {
private Point p1;
private Point p2;
private int innerCount;
private int outerCount;
public RectanglePanel() {
setBackground(Color.CYAN);
}
public void recordClick(Point p) {
if (p1 == null)
p1 = p;
else if (p2 == null) {
p2 = p;
if (p1.x > p2.x) {
int temp = p1.x;
p1.x = p2.x;
p2.x = temp;
}
if (p1.y > p2.y) {
int temp = p1.y;
p1.y = p2.y;
p2.y = temp;
}
} else if (inRectangle(p))
innerCount++;
else
outerCount++;
repaint();
}
private boolean inRectangle(Point p) {
return p.x >= p1.x && p.x <= p2.x && p.y >= p1.y
&& p.y <= p2.y;
}
public void reset() {
p1 = null;
p2 = null;
innerCount = 0;
outerCount = 0;
repaint();
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.drawString("count = " + outerCount,0, getHeight());
if (p1 != null && p2 != null) {
g2.setPaint(Color.RED);
Rectangle2D r = new Rectangle2D.Double(p1.x, p1.y,
p2.x - p1.x + 1,
p2.y - p1.y + 1);
g2.fill(r);
g2.setPaint(Color.BLACK);
g2.drawString("count = " + innerCount, p1.x, p2.y);
}
}
}
3. One possible solution appears below.
public class RectangleFrame {
private JFrame frame;
private RectanglePanel panel;
public RectangleFrame() {
frame = new JFrame();
frame.setSize(500, 200);
frame.setTitle("Rectangle fun");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
panel = new RectanglePanel();
frame.add(panel, BorderLayout.CENTER);
panel.addMouseListener(new MouseAdapter() {
public void mouseClicked(MouseEvent e) {
panel.recordClick(e.getPoint());
}
});
JButton b = new JButton("reset");
b.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
panel.reset();
}
});
JPanel p = new JPanel();
p.add(b);
frame.add(p, BorderLayout.SOUTH);
}
public void start() {
frame.setVisible(true);
}
}
]]>