Please help me...how to implement a class DateAndTime.java

Question

I have a class named DateAndTime.java How should I implement a method which allows me to check if the date entered by user is valid or not?. Also when the hour continues to a next day, how should I implement a method for a nextDay()? Thank you
class DateAndTime
     private int hour, minute, second, month, day, year;
     Constructor to initialize DateAndTime.
     Default DateAndTime 0:0:0 1/1/1
     public DateAndTime()
     {     month = 1;
          day =1;
          year =1;
     Constructor to set DateAndTime to specific values.
     Calls member function setDate and setTime to set variables.
     @param h hour of the DateAndTime
     @param m minute of the DateAndTime
     @param s second of the DateAndTime
     @param mo month of the DateAndTime
     @param d day of the DateAndTime
     @param y year of the DateAndTime
     public DateAndTime(int h, int m, int s, int mo, int d, int y)// CONSTRUCTOR
     {     if (isValidDate(mo, d, y))    //if date entered is valid, the date and time will be set
               setDate(mo, d, y);
               setTime(h, m, s);
          else
               System.out.println("Invalid Date :" + mo + "/" + d + "/" + y);
               setDate(1,1,1);
     Set the values of hour, minute, and second.
     @param h hour of the DateAndTime
     @param m minute of the DateAndTime
     @param s second of the DateAndTime
     public void setTime( int h, int m, int s ) //DEFINING SETTERS, SETTING time,hour,minute,and second,
     setHour( h );
     setMinute( m );
     setSecond( s );
     Set the hour if valid or to default 0.********************SET HOUR
     public void setHour( int h )
     {     hour = ( h >= 0 && h < 24 ) ? h : 0;     }
     Set the minute if valid or to default 0.******************SET MINUTE
     public void setMinute( int m )
     {     minute = ( m >= 0 && m < 60 ) ? m : 0;     }
     Set the hour if valid or to default 0. ******************SET SECOND
     public void setSecond( int s )
     {     second = ( s >= 0 && s < 60 ) ? s : 0;     }
     Set the values of month, day, and year.
     @param mo month of the DateAndTime
     @param d day of the DateAndTime
     @param y year of the DateAndTime
     public void setDate(int mo, int d, int y)//DEFINING SETTERS, SETTING DATE FOR month,day,and Year
          setMonth(mo);
          setDay(d,mo,y);
          setYear(y);
     Set the month if valid or to default 1. ****************SET MONTH
     public void setMonth(int mo)
     {     month = (mo >= 1 && mo <= 12)? mo : 1;  }
     Set the day if valid or to default 1. ****************SET DAY
     public void setDay(int d, int mo, int y) // ?????
     {     day = (isValidDate(mo,d,y))? d : 1;  }
     Set the year if valid or to default 1. ****************SET YEAR
     public void setYear(int y)
     {     year = (y >=1)? y : 1;     }
     Get the hour value.
     @return int
     public int getHour() {   return hour;  } //DEFINING GETTERS get hour, minute, second
     Get the minute value.
     @return int
     public int getMinute() {   return minute;  }
     Get the second value.
     @return int
     public int getSecond() {   return second;  }
     Get the month value.
     @return int
     public int getMonth() {   return month;  } //DEFINING GETTERS get month, day, and year
     Get the day value.
     @return int
     public int getDay() {   return day;  }
     Get the year value.
     @return int
     public int getYear() {   return year;  }
     Finds whether a given date is a valid date in A.D..
     @param mo month of the DateAndTime.
     @param d day of the DateAndTime.
     @param y year of the DateAndTime.
     @return boolean valid or not
     public static boolean isValidDate(int mo, int d, int y)
     //your code goes here
          return true;
     Print time DateAndTime in military format.
     public void printMilitary()
     System.out.println( month + "/" + day + "/" + year + "\t"
               + ( hour < 10 ? "0" : "" ) + hour + ":"
     + ( minute < 10 ? "0" : "" ) + minute);
     Formats DateAndTime for printing.
     @return String
     public String toString()
     return ( month + "/" + day + "/" + year + "\t"
               + (( hour == 0 || hour == 12 ) ? 12 : hour % 12)
     + ":" + ( minute < 10 ? "0" : "" ) + minute
     + ":" + ( second < 10 ? "0" : "" ) + second
     + ( hour < 12 ? " AM" : " PM" ));
     Increments DateAndTime by one second.
     Hint: calls nextDay() if tick() results in going in to next day.
     public void tick()
          //Your code goes here
second++;
if (second >59)
     second = 0;
     minute++;
if (minute > 59)
     minute = 0;
          hour++;
          if(hour >23)
     //      hour = 0;
     nextDay();
     Increments DateAndTime by one day.
     public void nextDay()
          day++;
          //your code goes here
}//end class

Answer 1

See java.util.Calendar
and java.util.GregorianCalendar
You can do all types of date validation with those classes.