PIC20A Final Exam

Instructions

The exam consists of 13 pages(including this page). You are responsible for checking the number of pages

Please read and answer all the questions carefully. The point value for each question in indicated. The total number of points available is 85. If you have trouble with a question, leave it and try another.

Unless otherwise stated, you may assume when code is given that the code compiles and is correct. When you are asked to write code, you are expected to write code in good style and with proper indentation.

Good luck!

Last Name:_________________	First Name:________________
Student ID:_________________

Question	Q1	Q2	Q3	Q4	Q5	Q6	Total(85pts)
Score

Q1(16pts) Write down the output of java ETest some arguments. If there is a new file created, write down the file name. Leave it blank if no file is created.

import java.io.*;

public class ETest {
    public static void main(String[] args) {
        String filename = null;
        int num;
        FileOutputStream out = null;
        
        try {           
           filename = args[0];  
           System.out.print(0);
           String temp = args[1];
           System.out.print(1);
           num = Integer.parseInt(args[1]);
           if(num == -1) {
               System.out.print(-1);
               out.write(9);
               System.out.print(9);
               System.exit(0);
           } else {
               System.out.print('X');
               out = new FileOutputStream(filename);
           }
           
           /* print out the first character 
           of the arguments
           starts from the second argment */
           for(int i = 0; i < num; i++) {
             // first character of args[i+2]
             System.out.print(args[i+2].charAt(0));
             out.write(args[i+2].charAt(0));
           }           
        } catch (NullPointerException ex) {
            System.out.print("A");
        } catch(ArrayIndexOutOfBoundsException ex) {
            System.out.print("B");
        } catch (NumberFormatException ex) {
            System.out.print("C");
        } catch(FileNotFoundException ex) {
            System.out.print("D");
        } catch (IOException ex) {
            System.out.print("E");
        }              
    }
}

(a)
java ETest
Output:____________________
File created:_______________
(b)
java ETest test1
Output:_____________________
File created:_______________
(c)
java ETest test2 abc
Output:_____________________
File created:_______________
(d)
java ETest folder 1 abc ,
here folder is the name of a folder
exists in the folder contains the program.
Output:_____________________
File created:_______________
(e)
java ETest test3 2 abc def ghi
Output:_____________________
File created:_______________
(f)
java ETest test4 -1 abc def ghi
Output:_____________________
File created:_______________
(g)
java ETest test5 3 xxx yyy
Output:_____________________
File created:_______________
(h)
java ETest test6 3 xxx yyy
The programs fails to write to the file.
Output:_____________________
File created:_______________
(i)
java ETest test7 2 aaa bbb
test7 already exists in the working folder.
Output:_____________________
File created:_______________

Q2(14pts)
(a)
Write down the output of java Picture?

import java.awt.*;
import javax.swing.*;

public class Picture extends JFrame {
    public void paint(Graphics g) {
        g.setColor(Color.red);
        g.fillOval(50,50,200,200);        
        g.setColor(Color.blue);
        g.fillOval(100,100,100,100);
        g.setColor(Color.green);
        g.drawRect(150,150,100,50);
        g.drawString("A", 150,150);
    }
    
    public static void main(String[] args) {
        Picture p = new Picture();
        p.setVisible(true);
        p.setSize(300,300);
    }
}

Answer

(b)
Consider the following file structures

 
folder1
   |
   +------folder2
   |        |
   |        +-------- file1 
   |        |
   |        +-------- file2 
   |
   |
   +------file3 
   |
   +------file4

What is the output of java FileTest ?

import java.io.*;

public class FileTest {
    public static void main(String[] args) {
        File f = new File("folder1");
        System.out.println(f.listFiles().length);
        System.out.println(f.exists());
        System.out.println(f.isFile());
    }
}

Answer:

(c)
I have 2 classes in 2 different files. What is the output after we run java Test?

public class Test {
   public static void main(String[] args) {
       Holder h = new Holder();
       h.held = 100;
       h.bump(h);
       System.out.println(h.held);
   }
}

public class Holder {
   public int held = 0;
   public void bump(Holder theHolder) {
     theHolder.held++;
   }
}

Answer

(d)
What is the output of java StringTest?

public class StringTest {
    public static void main(String[] args) {
        String s = "abcdeabcde";
        System.out.println(s.lastIndexOf("cd"));
        System.out.println(s.indexOf('X'));
        System.out.println(s.replace('c', 'X'));
        System.out.println(s.charAt(2));      
        s.toUpperCase();
        System.out.println(s);
    }
}

Answer:

(e)
What is the output of java SwingTest?

import java.awt.*;
import javax.swing.*;

public class SwingTest extends JFrame {
    Container contentPane = getContentPane();
    public SwingTest() {
        contentPane.setLayout(new GridLayout(2,3));
        for(char ch = 'a'; ch <= 'e'; ch++) {
            contentPane.add(new JLabel("" + ch));
        }
        JLabel label = new JLabel("X");
        contentPane.add(label,2);
    }
    
    public static void main(String[] args) {
        SwingTest test = new SwingTest();
        test.pack();
        test.setVisible(true);
    }
}

Answer:

Q3(10pts)
Circle error(s) of the following programs and write corrections beside them. If there is no error, write down no error.
(a)

import java.util.*;

public class Program1 {
    public static void main(String[] args) {
        Vector v = new Vector();
        int[] a = {1,2,3};
        for(int i = 0; i < 3; i++) {
            v.add(a[i]);
        }
    }
}

(b)

import java.util.*;

public class Program2 {
    public static void main(String[] args) {
        String[] s = {"A","B", "XYZ", "123"};
        Vector v = new Vector();
        for(int i = 0; i < s.length; i++) {
            v.add(s[i]);
        }
        
        Vector v2 = new Vector();
        for(int i = 0; i < 4; i++) {
            v2.add(v.get(i).toLowerCase());
        }
    }
    
}

(c)

import java.awt.*;
import javax.swing.*;
import java.util.*;

public class Program3 {
    public static void main(String[] args) {
        LinkedList list = new LinkedList();
        Object obj0 = Color.red;
        Object obj1 = Color.green;
        Object obj2 = Color.blue;
        list.add(obj0);
        list.add(obj1);
        list.add(obj2);
        JLabel[] labels = new JLabel[10];
        for(int i = 0; i < 20; i++) {
             labels[i].setBackground(list.get(i));
        }
    }
}

(d)

import java.io.*;

public class Program4 {
    public static void main(String[] args) {
       FileOutputStream out = new FileOutputStream("hi.txt");
       out.write(10);
       out.write('a');
    }
}

(e)

public class Program5 {
    public static void main(String[] args) {
        int a = Integer.parseInt(args[0]);
        int b = Integer.parseInt(args[1]);
        try {
            int result = a/b;
        } catch (Exception ex) {
            return;
        }
        
        if(result < 0) {
            System.out.println("Negative");
        } else {
            System.out.println("Positive");
        }
    }
}

Q4 (15pts)
(a)
Fill in the codes below. The equals(Object obj) returns true if and only if obj is Employee and they have the same ID.

public class Employee {
    public String ID; // 6 digit ID
    public String name;
    public char gender;
    public double salary;
    
    public Employee(String ID, String name, char gender, double salary) {
        this.ID = ID;
        this.name = name;
        this.gender = gender;
        this.salary = salary;
    }
    
    public boolean equals(Object obj) {
         // your codes
         





         





         





    }
}

(b)
Follows from part (a). Suppose Vector v is a Vector of Employees. Write a method to find the average salary of all the male (i.e. gender is 'M' or 'm') employee. Return 0 if there is no male employee.

public double averageSalary(Vector v) {
    // your codes
    










    





}

(c)
Suppose LinkedList list is a LinkedList of Doubles. Write a program to go through all the elements in the list, if the element is negative, set it to 0.

public void removeNegative(Vector v) {
   // your codes
   










   












}

Q5(15pts) You are going wo write a program named MoveSmiley.java

At the beginning of the program
When you click on the left arrow button(or right arrow button), the smiley face will move to the left (or right) by 1. If the smiley face is already at the leftmost button(or rightmost button), click the left arrow button(or right arrow button) has no effect.
Example: click on the right arrow button
When you click on any number button, the smiley face move to that button
Example: click on the 0 button
You have to use anonymous class for the actions of the number buttons
You have to use a seperate class for the actions of the left/right buttons.

Here are the image files

smiley.gif

left.gif

right.gif

Hint

to remove icon, use setIcon(null).
I use a method setIndex(int newIndex) to reset the index. You don't have to use my hint.

Answer:

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;

public class MoveSmiley extends JFrame {
    int currentIndex = 4;
    JButton[] buttons = new JButton[9];
    JButton leftButton = __________________________;
    JButton rightButton = _________________________;
   
    
    JPanel centerPanel = new JPanel(new GridLayout(1,0));
    JPanel southPanel = new JPanel(new GridLayout(1,0));
    
    // other variables
    








    
    public MoveSmiley() {
        super("Move smiley");
        for(int i = 0; i &llt; 9; i++) {
            buttons[i] = new JButton(Integer.toString(i));
            // your codes
            










            
            
            
            
            //Your must use anonymous class
            buttons[i].addActionListener(
            










            









         
            );
        } // end for loop 
     
        

        
        // use seperate classes for left button action and right button action
        leftButton.addActionListener(new Listener(this, "left"));
        rightButton.addActionListener(new Listener(this, "right"));
        
        
        southPanel.add(leftButton);
        southPanel.add(rightButton);
        
        getContentPane().add(centerPanel);
        getContentPane().add(southPanel, BorderLayout.SOUTH);
        // your codes (if any)
        










        










    } // end constructor
    
    // your codes(if any) 
    










    










    public static void main(String[] args) {
        MoveSmiley f = new MoveSmiley();       
        f.setSize(450,100);
        f.setVisible(true);
    }
}

// seperate class
class Listener implements ActionListener {
    MoveSmiley smiley;
    String direction; // "left" or "right"
    
    public Listener(MoveSmiley smiley,  String direction) {
        this.direction = direction;
        this.smiley = smiley;
    }
    
     // your codes for the action
     










     










     










}

Q6(15pts) I have my cell phone bill information in a file named bill.txt.
Here is an example

11/22/2003 # 15:40 # 1(310)222-3333 # 25
11/22/2003 # 18:40 # 1(310)444-5555 # 45
11/22/2003 # 22:30 # 1(818)111-2222 # 103
11/22/2003 # 23:10 # 1(323)444-5555 # 93
11/23/2003 # 3:00 # 1(323)222-4444 # 105
11/23/2003 # 9:20 # 1(310)222-3333 # 125
11/23/2003 # 10:43 # 1(310)444-5555 # 145
11/23/2003 # 13:30 # 1(818)111-2222 # 203
11/23/2003 # 13:50 # 1(323)444-5555 # 31
11/23/2003 # 19:23 # 1(510)111-8888 # 69
11/23/2003 # 20:45 # 1(626)888-9009 # 13

The format of the file is

date of the calling # time you made the call # phone number # minutes of the call

Each data is seperated by " # " (space sharp space).

The format of the time is hour:mins. They are in 24hours format.
If you made a call between 8:00 and 18:59 (before 19:00). Then you will be charged 0.25 per minute. Even if you made call at 18:59 and talk for 20 mins, you will still be charged for 20 mins.
Write a program to print out the amount you have to pay. Example: after you run java PhoneBill, the output of the DOS prompt is
You have to pay $168.25.
If your program ecounter an error during the program, print out
I can't process the file.
and exit the program.

import java.io.*;

public class PhoneBill {
    public static void main(String[] args) {
         // your codes
          




















          















          














     }
}