NumberDisplay

public class NumberDisplay
{
    private int limit;
    private int value;

    public NumberDisplay(int rollOverLimit)
    {
        limit = rollOverLimit;
        value = 0;
    }

    public int getValue()
    {
        return value;
    }

    public void setValue(int replacementValue)
    {
        if((replacementValue >= 0) && (replacementValue < limit))
        {
            value = replacementValue;
        }
    }

    public String getDisplayValue()
    {
        if(value < 10)
        {
            return "0" + value;
        }
        else
        {
            return "" + value;
        }
    }

    public void increment()
    {
        value = (value + 1) % limit;
    }
}