Java

OOP GUIDE / WORK

DURATION CLASS

Topics

• Instance variables, constructors, methods
• Using encapsulation

TASK – PART 1 – DURATION CLASS

You will create a Duration class which will hold the duration of something like a movie or a song. Here are the specifications:

• It has 3 private integers called hours, minutes and seconds.
  
  
• It has 3 constructors.
  
  
• Constructor #1 gets a value for each instance variable.
  
  
• Constructor #2 gets two integers, one for minutes and one for seconds. The value of hours is to be set to 0.
  
  
• Constructor #3 gets one integer for seconds. Both hours and minutes should be set to 0.
  
  
• It has the following instance methods:
  
  
• The method getTotalSeconds() returns the duration as total seconds. Remember that 1 hour has 3600 seconds and 1 minute has 60 seconds.
  
  
• The method toString() returns a String in the format AhBmCs where A is the hours, B is the minutes and C is the seconds. For example, a 2 hour 5 minute and 12 second duration would have a String representation of “2h5m12s”.

TASK – PART 2 – TESTING THE DURATION CLASS

Create a DurationTester class. Create three Duration objects each using a different constructor. Make sure to test the instance methods.

TASK – PART 3 – SHORT ANSWER QUESTIONS

a) Constructor #2 (and Constructor #3) can be accidentally misused. Can you predict how a programmer might make an error?

b) The method getTotalSeconds() requires a calculation that might be challenging for some. How would you test it to make sure that is working correctly like it is intended to be?