/**
 * We'll write our own version of the book's NumberDisplay class for 
 * practice. A NumberDisplay JUST keeps track of a two-digit number.
 * We'll eventually use two of these in the clock -- one for hours
 * and one for minutes.
 * 
 * @author Brad Richards
 * @version 1.0
 */
public class NumberDisplay
{

    private int value = 0;   // Always start this out at zero
    private int upperLimit;  // Number you can "never reach" -- 60 for minutes

    /**
     * Constructor that creates a NumberDisplay with the specified upper limit.
     * 
     * @param rollOverLimit The value at which the display should roll over.
     */
    public NumberDisplay(int rollOverLimit)
    {
        upperLimit = rollOverLimit;
    }

    /**
     * Increment increases the value of the clock by one, wrapping around if
     * necessary.
     */
    public void increment()
    {
        value = value + 1; // Increment the value
        if (value >= upperLimit) {  // Fix it if it got too large
            value = 0;
        }
    }

    /**
     * Returns a string version of the displayed value.  If it's a single digit, we
     * stick an extra zero in front of it.
     * 
     * @return Returns current value as a two-character string.
     */
    public String getDisplayValue()
    {
        if (value < 10) {
            return "0"+value;
        }
        else {
            return ""+value; 
        }
    }

    /**
     * A "getter" that returns the current display value.
     * 
     * @return Current value of NumberDisplay.
     */
    public int getValue()
    {
        return value; // For now...
    }

    /**
     * Sets the display to the specified value, as long as the specified value is
     * within the appropriate range.  Otherwise we print an error message and leave
     * the value unchanged.
     * 
     * @param newValue A new value that's >= 0 and < roll over limit.
     */
    public void setValue(int newValue)
    {
        if (newValue >= 0 && newValue < upperLimit) {
            value = newValue;
        }
        else {
            System.out.println("Proposed value is out of range! Ignoring request.");
        }
    }
}