Problem of the Day

Friday, November 13, 2026

Problem:

The Clock class tracks the current time, which can be displayed in either 24-hour mode (what some call "military time"), or 12-hour mode (where morning is "AM" and afternoon/evening is "PM"). A summary of some of the values in each mode is given here.

A partial listing of the Clock class is given here.

public class Clock
{

    private int currentHour; // an int from 0-23
    private boolean mode12;

    /* Constructor and some methods not shown */


    /**
     * Determines a version of the currentHour that is suitable
     * for display, depending on the mode that has been set
     * @return an hour 0-23 (if in 24-hour mode) or an AM-PM hour
     */
    public int getDisplayHour()
    {
        /* code not shown */
    }

}

Which of the following getDisplayHour methods will return the correct displayHour?

1. 
   

   public int getDisplayHour()
   {
       if (mode12)
           return currentHour % 12;
       else
           return currentHour;
   }

2. 
   

   public int getDisplayHour()
   {
       if (mode12)
           if (currentHour == 0)
               return 12;
           else
               return currentHour % 12;
       else
           return currentHour;
   }

3. 
   

   public int getDisplayHour()
   {
       if (mode12)
           if (currentHour % 12 == 0)
               return 12;
           else
               return currentHour % 12;
       else
           return currentHour;
   }

4. 
   

   public int getDisplayHour()
   {
       if (mode12)
           if (currentHour == 12)
               return 0;
           else
               return currentHour % 12;
       else
           return currentHour;
   }

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