Q1(32 pts)
a) 3pts.
Ouput 0
Do What?
Output 1
One Two
Output 2
Two
Output 3
Three Do What?
Output 4
Do What?
b) 2 pts
2,4
c) The question is cancelled
B.
The conversion in line 6 is fine(class to interface), but the conversion in line 7 (interface to class) is not allowed. A cast in line 7
will make the code compile, but then at runtime a ClassCastException will be thrown, because
Washer and Swampthing are incompatible.
d) 3 pts
10020
e) 2 pts
1,4
f) 2 pts
e
g) 10 pts
output 1
For loop
Error B 0
-1
output 2
For loop
End For Loop
2
output 3
For loop
End For Loop
Error D 0
-1
output 4
For loop
Error A 3
-1
output 5
For loop
Error C 2
-1
h) 5 pts
i) 5 pts
Q2 (20 pts)
a) 3 pts.
1pt for finding the error, 2 pts for correction.
Declare the class abstract or implement the missing method.
b) 3 pts.
public class ClassB {
int div(int a, int b) {
int result; // must declare it outside of other blocks.
try {
result = a/b;
} catch (ArithmeticException ex) {
System.out.println("something is wrong");
return 0;
}
return result;
}
}
c) 3 pts
import java.awt.*;
public class ClassC {
public static void main(String[] args) {
Color c = new Color(0.5f,0.5f,0.5f);
Color d = new Color(1,2,3);
Color e = d.red.blue.green; // this line is OK
}
}
d) 3 pts
import javax.swing.*;
public class ClassD {
public static void main(String[] args) {
JLabel[] label = new JLabel[5];
JFrame f = new JFrame();
for(int i = 0; i < 5; i++) {
label[i] = new JLabel();
label[i].setText("" + i); // or label[i].setText(Integer.toString(i))
f.getContentPane().add(label[i]);
}
}
}
e) 8 pts
1 pt for each method(total 5 pts). 1pt for each correction (total 3pts).
public class Test {
public void test1() {
Ex.methodA();
}
public void test2() {
try {
Ex.methodB();
} catch (ExceptionB ex) {
}
}
public void test3() {
try {
Ex.methodAB();
} catch (Exception B ex) {
}
}
public void test4() {
try {
Ex.methodAB();
} catch (ExceptionA ex) {
} catch(ExceptioinB ex) {
}
}
public void test5() {
try {
Ex.methodAB();
} catch (ExceptionB ex) {
}
}
}
Q3 (20 pts)
a) 10 pts, 2 pts for each change( 4 of them) 2 pts for no compiler error
public class Rewrite {
public static void main(String[] args) {
javax.swing.JFrame f = new javax.swing.JFrame("Hi");
f.getContentPane().setLayout(new java.awt.GridLayout(1,1));
f.getContentPane().add(new javax.swing.JLabel("abc"));
f.setSize(100,100);
f.setVisible(true);
}
}
b) 10 pts.
import java.io.*;
public class Count {
public static int Count(File file) {
File[] filelist = file.listFiles();
if(filelist == null ) {
return 0;
} else {
return file.listFiles().length;
}
}
}
or
import java.io.*;
public class Count {
public static int Count(File file) {
if(file.isDirectory()) {
File[] filelist = file.listFiles();
return file.listFiles().length;
} else {
return 0;
}
}
}
Q4 (28 pts)
a) 5 pts
b) 6 pts . 2 pts each
A : increase the number on display by 3.
B : increase the number on display by 2.
C : reset the number on display to 3.
c) 2 pts
8
d) 15 pts
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class ActionTest2 extends JFrame {
JButton buttonA = new JButton("A");
JButton buttonB = new JButton("B");
JButton buttonC = new JButton("C");
JLabel display = new JLabel("0", JLabel.CENTER);
Container contentPane = getContentPane();
public ActionTest2() {
contentPane.add(buttonA, BorderLayout.CENTER);
contentPane.add(buttonB, BorderLayout.EAST);
contentPane.add(buttonC, BorderLayout.WEST);
contentPane.add(display, BorderLayout.SOUTH);
buttonA.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
int num = Integer.parseInt(display.getText()) + 3;
display.setText("" + num);
}
});
buttonB.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
int num = Integer.parseInt(display.getText()) + 2;
display.setText("" + num);
}
});
buttonC.addActionListener( new ActionListener() {
public void actionPerformed(ActionEvent e) {
display.setText("" + 3);
}
});
}
public static void main(String[] args) {
ActionTest2 f = new ActionTest2();
f.setSize(200,100);
f.setVisible(true);
}
}
Q5 (25 pts)
import java.io.*;
public class TimeCal {
public static void main(String[] args) {
BufferedReader in = null;
PrintStream out = out = null;
try {
in = new BufferedReader(new FileReader(args[0]));
out = new PrintStream(new FileOutputStream(args[1]));
} catch (IOException ex) {
System.out.println("IOException");
System.exit(0);
}
String line = null;
String[] lineBreak;
int i = 0;
try {
while((line=in.readLine())!=null) {
lineBreak = line.split("-");
out.println(line + " " + ( second(lineBreak[1])- second(lineBreak[0])) + " seconds.");
}
} catch (IOException ex) {
System.exit(0);
}
try {
in.close();
out.close();
} catch (IOException ex) {
}
}
/** time is in hh:mm:ss format */
public static int second(String time) {
try {
String[] part = time.split(":");
int hh = Integer.parseInt(part[0]);
int mm = Integer.parseInt(part[1]);
int ss = Integer.parseInt(part[2]);
return 60*60*hh + 60*mm + ss;
} catch (Exception ex) {
return -1;
}
}
}
Q6 (25 pts)
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class ColorGame extends JFrame implements ActionListener {
private Color[] colors = {Color.red, Color.blue, Color.yellow, Color.green,
Color.pink, Color.black, Color.white, Color.orange};
private String[] name = {"red", "blue", "yellow", "green",
"pink", "black", "white", "orange"};
private JButton[] colorButton = new JButton[8];
private JLabel topLabel = new JLabel();
private JLabel correctLabel = new JLabel();
private JButton nextButton = new JButton("Next Question");
private JPanel colorPanel = new JPanel(new GridLayout(2,4));
private JPanel bottomPanel = new JPanel(new GridLayout(1,2));
private Container contentPane = getContentPane();
String currentColor;
public ColorGame() {
for(int i = 0; i < colorButton.length; i++) {
colorButton[i] = new JButton();
}
for(int i = 0; i < colorButton.length; i++) {
colorButton[i].setBackground(colors[i]);
colorButton[i].setActionCommand(name[i]);
colorButton[i].addActionListener(this);
colorPanel.add(colorButton[i]);
}
bottomPanel.add(correctLabel);
bottomPanel.add(nextButton);
currentColor = randomColor();
topLabel.setText(currentColor);
nextButton.addActionListener(this);
contentPane.add(topLabel, BorderLayout.NORTH);
contentPane.add(colorPanel);
contentPane.add(bottomPanel, BorderLayout.SOUTH);
}
public void actionPerformed(ActionEvent e) {
if(e.getSource() == nextButton) {
currentColor = randomColor();
topLabel.setText(currentColor);
correctLabel.setText("");
} else {
if(e.getActionCommand().equals(currentColor)) {
correctLabel.setText("Correct Color!");
} else {
correctLabel.setText("Wrong Color! Try Again!");
}
}
}
private String randomColor() {
return name[(int)(name.length*Math.random())];
}
public static void main(String[] args) {
ColorGame game = new ColorGame();
game.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
game.setSize(290,140);
game.setVisible(true);
}
}