8.7

//Date class declaration

public class Date
{
    private int month; // 1-12
    private int day; // 1-31 based on month
    private int year; // any year

    private static final int[] daysPerMonth = // days in each month
        { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

    //constructor: call checkMonth to confirm proper value for month;
    //call checkDay to confirm proper value for day
    public Date( int theMonth, int theDay, int theYear )
    {
        month = checkMonth( theMonth ); // validate month
        year = theYear; // could validate year
        day = checkDay( theDay ); // validate day

        System.out.printf(
            "Date object constructor for date %s\n", this);
    } // end Date constructor

    //utility method to confirm proper month value
    private int checkMonth( int testMonth )
    {
        if( testMonth > 0 && testMonth <= 12 ) //validate month
            return testMonth;
        else // month is invalid
            throw new IllegalArgumentException( "month must be 1-12" );
    } // end method checkMonth

    //utility method to confirm proper day value based on month and year
    private int checkDay( int testDay )
    {
        //check if day in range for month
        if( testDay > 0 && testDay <= daysPerMonth[ month ] )
            return testDay;

        //check for leap year
        if( month == 2 && testDay == 29 && ( year % 400 == 0 ||
            ( year % 4 == 0 && year % 100 != 0 ) ) )
          return testDay;

        throw new IllegalArgumentException(
            "day out-of-range for the specified month and year" );
    } // end method checkDay

    //return a String of the form month/day/year
    public String toString()
    {
        return String.format( "%d/%d/%d", month, day, year );
    } //end method toString
}//end class Date