Problem of the Day

Thursday, May 16, 2024

Problem:

The TimeKeeper class models a clock or watch that keeps track of the passage of time in a 24-hour cycle:

• at midnight it is 0 hours, 0 minutes, and 0 seconds
• at noon it is 12 hours
• one second before midnight it is 23 hours, 59 minutes, and 59 seconds

The tick method is called once a second, updating the instance variables appropriately. A partial implementation of the class is given here.

public class TimeKeeper
{
    private int hours;
    private int minutes;
    private int seconds;
    
    public TimeKeeper(int hours, int minutes, int seconds)
    {
        this.hours = hours;
        this.minutes = minutes;
        this.seconds = seconds;
    }
    
    /**
     * Adds one second to the clock and adjusts all three instance variables accordingly
     */
    public void tick()
    {
    
        /* missing code */
    
    }
    
    /* other methods not shown */
    
}

Which of the following could be used to replace /* missing code */ so that the tick method will work as intended?

1. 
   

   seconds += 1;
   if (seconds / 60 == 1) 
   {
       minutes += 1;
       seconds = seconds % 60;
   }
   if (minutes / 60 == 1) 
   {
       hours += 1;
       minutes = minutes % 60;
   }
   hours = hours % 24;

2. 
   

   seconds += 1;
   if (seconds / 60 == 1) 
   {
       minutes += 1;
       seconds = seconds / 60;
   }
   if (minutes / 60 == 1) 
   {
       hours += 1;
       minutes = minutes / 60;
   }
   hours = hours % 24;

3. 
   

   seconds += 1;
   if (seconds % 60 == 1) 
   {
       minutes += 1;
       seconds = seconds % 60;
   }
   if (minutes % 60 == 1) 
   {
       hours += 1;
       minutes = minutes % 60;
   }
   hours = hours % 24;

4. 
   

   seconds += 1;
   if (seconds / 60 == 1) 
   {
       minutes += 1;
       seconds = seconds % 60;
   }
   if (minutes / 60 == 1) 
   {
       hours += 1;
       minutes = minutes % 60;
   }
   hours = hours / 24;
   

5. 
   

   seconds += 1;
   if (seconds / 60 == 1) 
   {
       minutes += 1;
       seconds = seconds % 60;
   }
   if (minutes / 60 == 1) 
   {
       hours += 1;
       minutes = minutes % 60;
   }
   hours = 24 - hours;

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