Date Java

I'm using the eclipse software and I get an error for my porgramming for the Date.java..Please assist.Here's what I have so far:



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

// constructor: confirm proper value for month;
// call method function checkDay to confirm proper value for day.
public Date( int theMonth, int theDay, int theYear ) {
if ( theMonth > 0 && theMonth <= 12 ) // validate month
month = theMonth;
else {
month = 1;
System.out.println( "Month " + theMonth +
" invalid. Set to month 1." );
}
year = theYear;
day = checkDay ( theDay ); // validate day
System.out.println("Date object constructor for date "+ toString() );
}

// utility method to confirm proper day value based on month and year.
public int checkDay( int testDay ) {
int daysPerMonth[] =
{ 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
// 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;
System.out.println( "Day " + testDay + " invalid. Set to day 1." );
return 1; // leave object in consistent state
}
// increment the day and check if doing so will change the month
public void nextDay() {
// implement the nextDay method here!!!!
}

// create a String of the form month/day/year
public String toString() {
return month + "/" + day + "/" + year;
}

} // end class Date


public class DateTest {
public static void main( String args[] ){
System.out.println( "Checking increment" );
Date testDate = new Date( 11, 27, 1988 );
// test incrementing of day, month and year
for ( int counter = 0; counter < 40; counter++ ) {
testDate.nextDay();
System.out.println( "Incremented Date:" + testDate.toString() );
}
}
}