Final 1

Q1. (5 pts) Write a method int numOfChar(JTextField textfield). It returns the number of characters of the text in the textfield.

int numOfChar(JTextField textfield) {
    // your codes here

    
}

Q2. (10 pts) Consider the following code

public class Bruin {
    private String name;
    private String studentID;
    
    public Bruin(String name, String studentID) {
	this.name = name;
	this.studentID = studentID;
    }
    
    /** return true if obj is a Bruin and has the same student ID */
    public boolean equals(Object obj) {
	if(obj instanceof Bruin) {
	    return studentID.equals(((Bruin)obj).studentID);
	} else {
	    return false;
	}
    }
    
    public String toString() {
	return "Name : " + name + "\nStudent ID : " + studentID;
    }
}

(a) What is the output of the following lines


        Bruin b1 = new Bruin("Charles", "102222333");
        System.out.println(b1);

(b) Consider the following code, write down the output of the following program

import java.util.*;

public class LinkedListTest {
    public static void main(String[] args) {
	LinkedList list = new LinkedList();
        Bruin b1 = new Bruin("Charles", "102222333");
        Bruin b2 = new Bruin("Amy", "202333444");
        Bruin b3 = new Bruin("Betty", "902555666");
        list.add(b1);
        list.add(b2);
        list.add(b3);
        list.add(new Bruin("Mike", "222333444")); 
        list.add(new Bruin("Eve", "733444555"));
        list.add(new Bruin("Dave", "333222111"));
	
        list.remove(b2);
        System.out.println("Output1:");
        System.out.println(list.get(1));
	
        list.set(2, new Bruin("Charles", "123456789"));
        list.removeFirst();
        System.out.println("Output2:");
        for(int i = 1; i <= 3; i++){
            System.out.println(list.get(i));
        }
	
        System.out.println("Output3:");
        System.out.println(list.contains(b1));
	
        System.out.println("Output4:");
        System.out.println(list.indexOf(new Bruin("Charles", "123456789")));
	
        System.out.println("Output5:");
        System.out.println(list.indexOf(new Bruin("Unknown", "333222111")));
    }
}

Write the output below.

Q3.(25pts) Write a class CheckBoxTest, it has 5 JCheckBox and 1 JLabel. The JLabel displays the number of JCheckBox checked.

At the beginning
After you click checkbox 3 and 5.
After you uncheck checkbox 5.

Hint: write a method int countChecked(). It returns the number of checkbox checked.
Here is part of the code. You can implements interfaces after the class declaration.

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

public class CheckBoxTest extends JFrame               
{
    // write your codes here


   
    
    


    public static void main(String[] args) {
        JFrame f = new CheckBoxTest();
	f.pack();
	f.setVisible(true);
	f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}

Q4.(35pts)
(a) Describe 2 ways to create Threads ? (extends/implements what classes? override which method(s), how to start threads? What happens when you start threads?)

(b) Create a class name SleepThread.
It is a thread with 2 members: int sleepTime and String name. The thread displays name in every sleepTime seconds.
Write the main method, so that it displays my name ("Charles") in every 3 seconds. Displays Mike's name ("Mike") in every 7 seconds. Displays Michelle's name ("Michelle") in every 10 seconds.
Here is the output of the program.

Charles     
Charles  
Mike 
Charles
Michelle 
Charles 
Mike
Charles 
Charles
Michelle  
(keep going ....)

I write down the time to help you understand the program (the time is not part of the output).

Charles  (3s)   
Charles  (6s)
Mike     (7s)
Charles  (9s)
Michelle (10s)
Charles  (12s)
Mike     (14s)
Charles  (15s)
Charles  (18s)
Michelle (20s)
(keep going.....)

Here is part of the code. You can implements interfaces or extends class after the class declaration.

public class SleepThread  extends Thread                   
{
    public String name;
    public int sleepTime;
    
    public SleepThread(String name, int sleepTime) {
        this.name = name;
        this.sleepTime = sleepTime;
    }    
    
    public void run() {
        while(true) {
	   try {
	      sleep(sleepTime*1000);
	    }
	 }
    }
	      
    

    
    
    
    public static void main(String[] args) {
       // your code
       
       
    }
}

final1 Q5.(25 pts) Write a program, create a JFrame.

When you click a point, the coordinate shows up near the point.
When you click another point, a straight line shows up.
Click one more point. The coordinate shows up again. Click another point to make a straight line.
Repeat the process. We get different straight lines.

Click the first point.
Click the second point.
Click the third point.
Click the fourth point.
The process continues ...

Here is part of the code. You can implements interfaces or extends class after the class declaration.

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

public class DrawLine extends JFrame  
{
    private static int NO_POINT = 0;
    private static int ONE_POINT = 1;
    private static int TWO_POINTS = 2;
    private int state = NO_POINT;
    private Color color = Color.black;
    // some other variables 



    
    
    
    public void paint(Graphics g) {
        // your codes here
    

    
    
    }
    // your codes

    
    
    // main method
    public static void main(String[] args) {
        JFrame f = new DrawLine();
	f.setTitle("Draw Line");
	f.setSize(500,200);
	f.setVisible(true);
	f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}