CS 110: Lab 6

Learning Objectives

After completion of this lab, you should be able to

Work collaboratively as a pair programming team
Use test-driven development for developing software programs
Use type casting to convert doubles to integers
Define a Java class to format double values as a string
Test your class with a main method
Use your class in a graphical user interface (GUI) Windows program
Test a program as an independent tester
Read and modify a program written by someone else

Work collaboratively as a pair programming team

All labs in CS 110 will be done as pair programming teams. Your partner for today's lab is listed in the table below:

Hebeler 203
Grader: Vinh Tran; Assistant: Daniel Carpenter
Team 1 Aguilar Jr, Jaime Field, Sarah	Team 2 Amezcua Gutierrez, Edson Hansen, Mitchell	Team 3 Baird, Owen Hastings, Jake	Team 4 Berman, Jake Hogan, Martin	Team 5 Coudriet, Blake Ling, Nathan
Team 6 Erickson, Joel Nash, Chris	Team 7 Goeke, Max Olivares, Scott	Team 8 Harris, Alexander Shearer, Stetson	Team 9 Heflick, Liz Wagster, Nathan	Team 10 McCauley, Rylee Smith, Stephanie
Team 11 Millard, Ryan Akana, Chris	Team 12 Olden, Greg Awan, Samara	Team 13 Quayle, Weston Barrett Wright, Matthew	Team 14 Straub-Walden, Andy Bloom, Thomas	Team 15 Williamson, Sarah Cuddington, Chris
Fill in: Millard, Mike

Note: Partners will change every week.

You may wish to review basic pair programming guidelines before you begin.

Partners sit side-by-side at one computer, sharing the keyboard, mouse, and monitor
One team member (the driver) has control of the keyboard/mouse and actively implements the program
The other team member (the navigator) continuously observes the work of the driver to identify tactical defects (such as syntactic and spelling errors, etc.) and also thinks strategically about the direction of the work

You should change roles every 10 to 15 minutes.

Introduction

You will write a Java class called Seconds that converts a time value represented in seconds (double) to its equivalent time value as a String

For example, the time 69.752 (in seconds) would be represented as the String "1:9.752" or 1 minute, 9 seconds, and 752 milliseconds (in minutes:seconds.milliseconds).

Use test-driven development for developing software programs

Begin by developing test cases for this program.

Test Cases
Time (in seconds)	Time
Time (in seconds)	minutes	seconds	milliseconds
69.752	1	9	752
336.219	5	36	219
542.200
226.987
85.333

Write your calculated test case values in the Lab assignment sheet. You will turn in this sheet at the end of lab for credit.

Use type casting to convert doubles to integers

In the test cases, time (in seconds) is represented as a double value. The part to the left of the decimal represents the total seconds, the part to the right of the decimal represents the milliseconds.

Converting a double to an integer value in Java is done with the cast operator. For example, to convert the double variable d to the integer i, we could write

double d;
int i;

d = 336.219;
i = (int) d;

In this case, i would be set to 336

To get at the decimal part of 336.219, we could use a combination of multiplication, casting, and the modulus operator

double d = 336.219;
int fractionalPart;

fractionalPart = ((int) (d * 1000)) % 1000;

In this case, fractionalPart would equal 219

Define a Java `class` to format double values as a string

Create the Java class Seconds and save as Seconds.java
Class Seconds needs a constructor method and has one instance method, format(), that returns a String formatted as minutes:seconds.milliseconds

public class Seconds
{
// instance variable
double time;

// Constructor method
public Seconds (double t)
{
time = t;
}

// returns time formatted as minutes:seconds.milliseconds
public String format()
{
// Declare local variables
String timeString;
int minutes;
int seconds;
int milliseconds;

// Calculate minutes, seconds, milliseconds
// Hint: use type casting to convert time from double to int
// You figure out this part

// Create the string minutes:seconds.milliseconds using concatenation
// You figure out this part

return timeString;
}
}

Test your class with a main method

A short main method will be used for testing purposes.

Save the main method shown below to a new file named TestSeconds.java
Compile and test your program, comparing the formatted time strings it produces with your hand-calculated values

import java.util.Scanner;

public class TestSeconds
{
public static void main(String args[])
{
// local variable
double localTime;

// Create a Scanner object
Scanner keyboard = new Scanner(System.in);

// Get a time in seconds from the user
System.out.print("Enter a time in seconds: ");
localTime = keyboard.nextDouble();

// Create a new Seconds object
Seconds time = new Seconds(localTime);

// Display the local time formatted as a string
System.out.println(time.format());
}
}

Sample Session

Enter a time in seconds: 336.219
5:36.219

Use your class in a graphical user interface (GUI) Windows program

Once your class is tested and determined to be working correctly, we will use it to format time (as a double) into a strings to display in a graphical user interface (GUI) Windows application acting as a stopwatch.

Download and save in your U:\labs\lab6 folder the following two Java files
- StopWatch.java file to implement the start and end times for a stopwatch
- StopWatchGui.java to create a graphical user interface for the stopwatch
- Note: you are not expected to understand the code yet, creating GUI Java applications is a topic of CS 111
Compile and run the StopWatchGui class and confirm that the stopwatch is working correctly
- Note: you should not need to make any changes to your tested TimeFormat class code

startup with no buttons pressed start button pressed stop button pressed

Test a program as an independent tester

Java programs need to be thoroughly tested before being sold or released to the public.

The best testers are usually independent testers, or those who did not write the source code. It has been shown that developer of the source code overlook many bugs while testing because they are not thorough or they make false assumptions about using the program that independent testers often catch as errors.

Even though the user interface to the stopwatch program is very simple, it has subtle errors.

Test the stopwatch program as an independent tester and find the error(s)
- You are testing the program by running it and looking at its output, not be carefully looking inside the source code for coding errors

Read and modify a program written by someone else

Examine the code that you downloaded and added to your lab6 folder. StopWatchGui.java contains the code that creates the graphical user interface that displays as a window application.

A problem occurs with the stopwatch program when the user clicks on the stop button without clicking the start button first. (Try it if you did not discover this problem in the previous activity)

One way to fix the problem (as a programmer) is to design the user interface to initially disable the Stop button to prevent the user for clicking it before they clicked the Start button. To disable or enable a button, use the button's setEnabled() method, passing a true or false value as the method argument.

// Disable the stop button
stopButton.setEnabled(false);

Look through the StopWatchGui.java code and find where the Stop button is created.
Add the line to disable the Stop button
- Test the program and verify that the Stop button is initially disabled
Look through the StopWatchGui.java code find where the method called when the user clicks on the Start button
- Add the line to enable the Stop button
Thoroughly test the program - there are still errors you should fix

To Receive Credit

By showing up on time for lab, working collaboratively with your pair partner on the lab solution, and staying to the end of the class period, you receive full credit for the lab assignment.
- Copy the contents of the lab folder to the partner's USB thumb drive (or email it to them if they do not have a thumb drive).
- Turn in the Lab assignment sheet to your TA to receive credit for the lab
  - Include both partners' names and the test case tables and formulas filled out
If you are unable to attend Today's lab,
- Print out the Lab 6 Assignment Sheet, write you name and account number on the sheet
- Write the program on your own, individually, (not using pair programming)
- Run your program and confirm that your program's output is correct
- Save the work to your U:\labs\lab6 folder and turn in the Lab 6 assignment sheet at the start of the next lab
  - Your grader will check your work in your CS 110 account

You are allowed to drop one lab grade for the entire quarter.

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