Month.java

package org.sigmah.shared.util;

/*
 * #%L
 * Sigmah
 * %%
 * Copyright (C) 2010 - 2016 URD
 * %%
 * This program 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.
 * 
 * This program 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 this program.  If not, see
 * <http://www.gnu.org/licenses/gpl-3.0.html>.
 * #L%
 */

import java.io.Serializable;

/**
 * Encapsulates a Gregorian month
 *
 * @author Alex Bertram
 * @author Denis Colliot (dcolliot@ideia.fr)
 */
public class Month implements Serializable, Comparable<Month> {

	/**
	 * Serial version UID.
	 */
	private static final long serialVersionUID = -8850584104362115311L;

	private int year;
	private int month;

	/**
	 * Constructs an uninitialized <code>Month</code>
	 */
	public Month() {
		// Serialization.
	}

	/**
	 * Constructs a <code>Month</code> at the given month and year. If month is outside of the range 1..12, the values are
	 * normalized. For example, <code>Month(2001, 13)</code> initalizes this <code>Month</code> to January, 2002.
	 *
	 * @param year
	 *          Gregorian year (for example, 1999, 2009)
	 * @param month
	 *          Gregorian month (january=1, feb=2, ... dec=12)
	 */
	public Month(int year, int month) {
		this.year = year;
		this.month = month;

		while (this.month > 12) {
			this.year++;
			this.month -= 12;
		}
		while (this.month < 1) {
			this.year--;
			this.month += 12;
		}
	}

	/**
	 * Gets this <code>Month</code>'s year
	 *
	 * @return the month's year.
	 */
	public int getYear() {
		return year;
	}

	/**
	 * Sets this <code>Month</code>'s year.
	 *
	 * @param year
	 *          Gregorian year (for example, 1999, 2009)
	 */
	public void setYear(int year) {
		this.year = year;
	}

	/**
	 * Gets this month
	 *
	 * @return The Gregorian month (1=january, 12=december)
	 */
	public int getMonth() {
		return month;
	}

	/**
	 * Sets this month
	 *
	 * @param month
	 *          The Gregorian month (1=january, 12=december)
	 */
	public void setMonth(int month) {
		this.month = month;
	}

	/**
	 * Compares this <code>Month</code> to another month
	 *
	 * @param m
	 *          The <code>Month</code> with which to compare this <code>Month</code>
	 * @return 0 if this month is the same as <code>m</code>, -1 if this month is earlier than <code>m</code>, or +1 if
	 *         this month follows <code>m</code>
	 */
	@Override
	public int compareTo(Month m) {
		if (year < m.year) {
			return -1;
		}
		if (year > m.year) {
			return 1;
		}
		if (month < m.month) {
			return -1;
		}
		if (month > m.month) {
			return 1;
		}
		return 0;
	}

	/**
	 * Returns a string representation of this Month in the format 2009-1
	 *
	 * @return a string representation of this Month in the format 2009-1, 2009-12
	 */
	@Override
	public String toString() {
		return year + "-" + month;
	}

	/**
	 * Parses a string in the format 2009-1, 2009-03, 2009-12 and returns the value as a <code>Month</code>
	 *
	 * @param s
	 *          The <code>String</code> to parse
	 * @return The value of the string as a <code>Month</code>
	 */
	public static Month parseMonth(String s) {
		String[] tokens = s.split("-");
		if (tokens.length != 2) {
			throw new NumberFormatException();
		}

		return new Month(Integer.parseInt(tokens[0]), Integer.parseInt(tokens[1]));
	}

	@Override
	public boolean equals(Object o) {
		if (this == o) {
			return true;
		}
		if (o == null || getClass() != o.getClass()) {
			return false;
		}

		Month month1 = (Month) o;

		if (month != month1.month) {
			return false;
		}
		if (year != month1.year) {
			return false;
		}

		return true;
	}

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

	public Month plus(int count) {
		return new Month(year, month + count);
	}

	public Month next() {
		return plus(+1);
	}

	public Month previous() {
		return plus(-1);
	}

	public static int monthsBetween(Month startMonth, Month endMonth) {
		return (endMonth.month - startMonth.month) + ((endMonth.year - startMonth.year) * 12);
	}
}