Note that the code in the Date object should take care of parsing the line. The

Question

Note that the code in the Date object should take care of parsing the line. The Date class needs a toString function that returns a String with the correct information.

To test whether one Date is before or equal to another Date, the Date class should have a compareTo function. The Date class should start with a line like:

The header for the compareTo method should have a header like:

This method should return -1 if this Date is before the other Date, 0 if they are equal, and +1 if this Date is after the other Date.

Explanation / Answer

working java code

public class Date implements Comparable<Date> {
private static final int[] DAYS = { 0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

private final int month; // month (between 1 and 12)
private final int day; // day (between 1 and DAYS[month]
private final int year; // year

public Date(int month, int day, int year) {
if (!isValid(month, day, year)) throw new IllegalArgumentException("Invalid date");
this.month = month;
this.day = day;
this.year = year;
}

/**
* Initializes new date specified as a string in form MM/DD/YYYY.
* @param date the string representation of this date
* @throws IllegalArgumentException if this date is invalid
*/
public Date(String date) {
String[] fields = date.split("/");
if (fields.length != 3) {
throw new IllegalArgumentException("Invalid date");
}
month = Integer.parseInt(fields[0]);
day = Integer.parseInt(fields[1]);
year = Integer.parseInt(fields[2]);
if (!isValid(month, day, year)) throw new IllegalArgumentException("Invalid date");
}

/**
* Return the month.
* @return the month (an integer between 1 and 12)
*/
public int month() {
return month;
}

/**
* Returns the day.
* @return the day (an integer between 1 and 31)
*/
public int day() {
return day;
}

/**
* Returns the year.
* @return the year
*/
public int year() {
return year;
}

// is the given date valid?
private static boolean isValid(int m, int d, int y) {
if (m < 1 || m > 12) return false;
if (d < 1 || d > DAYS[m]) return false;
if (m == 2 && d == 29 && !isLeapYear(y)) return false;
return true;
}

// is y a leap year?
private static boolean isLeapYear(int y) {
if (y % 400 == 0) return true;
if (y % 100 == 0) return false;
return y % 4 == 0;
}

/**
* Returns the next date in the calendar.
*
* @return a date that represents the next day after this day
*/
public Date next() {
if (isValid(month, day + 1, year)) return new Date(month, day + 1, year);
else if (isValid(month + 1, 1, year)) return new Date(month + 1, 1, year);
else return new Date(1, 1, year + 1);
}

/**
* Compares two dates chronologically.
*
* @param that the other date
* @return <tt>true</tt> if this date is after that date; <tt>false</tt> otherwise
*/
public boolean isAfter(Date that) {
return compareTo(that) > 0;
}

/**
* Compares two dates chronologically.
*
* @param that the other date
* @return <tt>true</tt> if this date is before that date; <tt>false</tt> otherwise
*/
public boolean isBefore(Date that) {
return compareTo(that) < 0;
}

@Override
public int compareTo(Date that) {
if (this.year < that.year) return -1;
if (this.year > that.year) return +1;
if (this.month < that.month) return -1;
if (this.month > that.month) return +1;
if (this.day < that.day) return -1;
if (this.day > that.day) return +1;
return 0;
}

/**
* Returns a string representation of this date.
*
* @return the string representation in the format MM/DD/YYYY
*/
@Override
public String toString() {
return month + "/" + day + "/" + year;
}

/**
* Compares this date to the specified date.
*
* @param other the other date
* @return <tt>true</tt> if this date equals <tt>other</tt>; <tt>false</tt> otherwise
*/
@Override
public boolean equals(Object other) {
if (other == this) return true;
if (other == null) return false;
if (other.getClass() != this.getClass()) return false;
Date that = (Date) other;
return (this.month == that.month) && (this.day == that.day) && (this.year == that.year);
}

@Override
public int hashCode() {
int hash = 17;
hash = 31*hash + month;
hash = 31*hash + day;
hash = 31*hash + year;
return hash;
}

public static void main(String[] args) {
Date today = new Date(2, 25, 2004);
StdOut.println(today);
for (int i = 0; i < 10; i++) {
today = today.next();
StdOut.println(today);
}

StdOut.println(today.isAfter(today.next()));
StdOut.println(today.isAfter(today));
StdOut.println(today.next().isAfter(today));

Date birthday = new Date(10, 16, 1971);
StdOut.println(birthday);
for (int i = 0; i < 10; i++) {
birthday = birthday.next();
StdOut.println(birthday);
}
}

}

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