de.knurt.fam.core.util.time.CalendarUtil.java Source code

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Here is the source code for de.knurt.fam.core.util.time.CalendarUtil.java

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/*
 * Copyright 2009-2012 by KNURT Systeme (http://www.knurt.de)
 *
 * Licensed under the Creative Commons License Attribution-NonCommercial-ShareAlike 3.0 Unported;
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://creativecommons.org/licenses/by-nc-sa/3.0/
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package de.knurt.fam.core.util.time;

import java.util.Calendar;
import java.util.Date;

import org.apache.commons.lang.time.DateUtils;

/**
 * simple calendar util functions
 * 
 * @author Daniel Oltmanns
 * @since 1.5.0 (09/13/2011)
 */
public class CalendarUtil {

    /** one and only instance of CalendarUtil */
    private volatile static CalendarUtil me;

    /** construct CalendarUtil */
    private CalendarUtil() {
    }

    /**
     * return the one and only instance of CalendarUtil
     * 
     * @return the one and only instance of CalendarUtil
     */
    public static CalendarUtil getInstance() {
        if (me == null) {
            //  no instance so far
            synchronized (CalendarUtil.class) {
                if (me == null) {
                    //  still no instance so far
                    //  the one and only me
                    me = new CalendarUtil();
                }
            }
        }
        return me;
    }

    /**
     * short for {@link #getInstance()}
     * 
     * @return the one and only instance of CalendarUtil
     */
    public static CalendarUtil me() {
        return getInstance();
    }

    /**
     * return the number of days between the given to calendar instances. the
     * result is always a positive long value.
     * 
     * @param c1
     *            first calendar instance
     * @param c2
     *            second calendar instance
     * @return the number of days between the given to calendar instances
     */
    public long daysBetween(Calendar c1, Calendar c2) {
        long result = 0l;
        while (!DateUtils.isSameDay(c1, c2)) {
            result++;
            if (c1.before(c2)) {
                c1.add(Calendar.DAY_OF_YEAR, 1);
            } else {
                c2.add(Calendar.DAY_OF_YEAR, 1);
            }
        }
        return result;
    }

    public long daysBetween(Calendar c, Date d) {
        Calendar dc = Calendar.getInstance();
        dc.setTime(d);
        return this.daysBetween(c, dc);
    }
}