Below is the syntax highlighted version of Date.java.
/****************************************************************************** * Compilation: javac Date.java * Execution: java Date * Dependencies: StdOut.java * * An immutable data type for dates. * ******************************************************************************/ package edu.princeton.cs.algs4; /** * The {@code Date} class is an immutable data type to encapsulate a * date (day, month, and year). * <p> * For additional documentation, * see <a href="https://algs4.cs.princeton.edu/12oop">Section 1.2</a> of * <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne. * * @author Robert Sedgewick * @author Kevin Wayne */ 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 /** * Initializes a new date from the month, day, and year. * @param month the month (between 1 and 12) * @param day the day (between 1 and 28-31, depending on the month) * @param year the year * @throws IllegalArgumentException if this date is invalid */ 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 {@code true} if this date is after that date; {@code false} otherwise */ public boolean isAfter(Date that) { return compareTo(that) > 0; } /** * Compares two dates chronologically. * * @param that the other date * @return {@code true} if this date is before that date; {@code false} otherwise */ public boolean isBefore(Date that) { return compareTo(that) < 0; } /** * Compares two dates chronologically. * * @return the value {@code 0} if the argument date is equal to this date; * a negative integer if this date is chronologically less than * the argument date; and a positive integer if this date is * chronologically after the argument date */ @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 {@code true} if this date equals {@code other}; {@code false} 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); } /** * Returns an integer hash code for this date. * * @return an integer hash code for this date */ @Override public int hashCode() { return day + 31*month + 31*12*year; } /** * Unit tests the {@code Date} data type. * * @param args the command-line arguments */ 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); } } } /****************************************************************************** * Copyright 2002-2022, Robert Sedgewick and Kevin Wayne. * * This file is part of algs4.jar, which accompanies the textbook * * Algorithms, 4th edition by Robert Sedgewick and Kevin Wayne, * Addison-Wesley Professional, 2011, ISBN 0-321-57351-X. * http://algs4.cs.princeton.edu * * * algs4.jar is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * algs4.jar is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with algs4.jar. If not, see http://www.gnu.org/licenses. ******************************************************************************/