increment date

public class Calendar
{
    private int[] monthDay = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    private String[] monthName = {"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
    
    private int day, month, year;
    
    public Calendar(int d, int m, int y)
    {
        year = y;
        month = m;
        day = d;
    }
    
    public boolean leapYear(int year)
    {
        boolean ans = false;
        
        if(year % 4 == 0)
        {
            ans = true;
        }
        
        if(year % 100 == 0)
        {
            ans = false;
        }
        
        if(year % 400 == 0)
        {
            ans = true;
        }
        
        return ans;
    }
    
    public void incrementDate()
    {
         day = day + 1;
         
         if(month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10 || month == 12)
         {
             if(day > 31)
             {
                 month = month + 1;
                 day = 1;
             }
         }
         
         if(month == 4 || month == 6 || month == 9 || month == 11)
         {
             if(day > 30)
             {
                 month = month + 1;
                 day = 1;
             }
         }
         
         if(month == 2)
         {
             if (leapYear(year))
             {
                 if(day > 29)
                 {
                     month = month + 1;
                     day = 1;
                 }
             }
             else 
             {
                 if(day > 28)
                 {
                    month = month +1;
                    day = 1;
                 }
             }
         }
         if(month > 12)
         {
             month = 1;
             year = year + 1;
            }        
    }
    
    public void decrementDate()
    {
         day = day - 1;
         
         if(day < 1)
         {
             month = month - 1;
             if(month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10 || month == 12)
             {
                     day = 31;
             }
             
             if(month == 4 || month == 6 || month == 9 || month == 11)
             {
                     day = 30;
             }
             
             if(month == 2)
             {
                 if (leapYear(year))
                 {
                         day = 29;
                 }
                 else 
                 {
                        day = 28;
                 }
             }
         
             if(month < 1)
             {
                 month = 12;
                 year = year - 1;
                 day = 31;
             }
         }
    }
}