java日期时间工具类比较常用，也比较基础，源码如下，希望对你有所帮助：

package com.cn.itcdns.util;

import org.apache.commons.lang.StringUtils;
import org.apache.commons.lang.time.DateFormatUtils;

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class DateUtil {

    /**
     * yyyy年MM月dd日
     */
    public static final String FormatDayToChinaTime24H = "yyyy年MM月dd日";
    /**
     * yyyy-MM-dd HH:mm:ss
     */
    public static String DATETIME_FORMAT = "yyyy-MM-dd HH:mm:ss";
    /**
     * yyyy-MM-dd
     */
    public static String DATE_FORMAT = "yyyy-MM-dd";
    /**
     * yyyyMMdd
     */
    public static String DATE_FORMAT1 = "yyyyMMdd";
    /**
     * HH:mm:ss
     */
    public static String TIME_FORMAT = "HH:mm:ss";
    /**
     * yyyyMMddHHmmss
     */
    public static String DATETIME_FORMAT2 = "yyyyMMddHHmmss";

    /**
     * 返回年份
     *
     * @param date
     *            日期
     * @return 返回年份
     */
    public static int getYear(Date date) {
        Calendar c = Calendar.getInstance();
        c.setTime(date);
        return c.get(Calendar.YEAR);
    }

    /**
     * 返回月份
     *
     * @param date
     *            日期
     * @return 返回月份
     */
    public static int getMonth(Date date) {
        Calendar c = Calendar.getInstance();
        c.setTime(date);
        return c.get(Calendar.MONTH) + 1;
    }

    /**
     * 返回日份
     *
     * @param date
     *            日期
     * @return 返回日份
     */
    public static int getDay(Date date) {
        Calendar c = Calendar.getInstance();
        c.setTime(date);
        return c.get(Calendar.DAY_OF_MONTH);
    }

    /**
     * Parse date like "yyyy-MM-dd".
     */
    public static Date parseDate(String d) {
        try {
            return new SimpleDateFormat(DATE_FORMAT).parse(d);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }
    /**
     * Parse date like "yyyyMMdd".
     */
    public static Date parseDate1(String d) {
        try {
            return new SimpleDateFormat(DATE_FORMAT1).parse(d);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }
    /**
     * Parse date like "yyyy-MM-dd HH:mm:ss".
     */
    public static Date parseDateTime(String d) {
        try {
            return new SimpleDateFormat(DATETIME_FORMAT).parse(d);
        } catch (Exception e) {
        }
        return null;
    }
    /**
     * Parse date like "yyyyMMddHHmmss".
     */
    public static Date parseDateTime2(String d) {
        try {
            return new SimpleDateFormat(DATETIME_FORMAT2).parse(d);
        } catch (Exception e) {
        }
        return null;
    }

    /**
     * Parse date like "HH:mm:ss".
     */
    public static Date parseTime(String d) {
        try {
            return new SimpleDateFormat(TIME_FORMAT).parse(d);
        } catch (Exception e) {
        }
        return null;
    }

    /**
     * 取得指定月份的最后一天
     *
     * @param strdate
     *            String
     * @return String
     */
    public String getMonthEnd(String strdate) {
        Date date = parseDate(getMonthBegin(strdate));
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        calendar.add(Calendar.MONTH, 1);
        calendar.add(Calendar.DAY_OF_YEAR, -1);
        return formatDate(calendar.getTime());
    }

    /**
     * 取得指定月份的第一天
     *
     * @param strdate
     *            String
     * @return String
     */
    public String getMonthBegin(String strdate) {
        Date date = parseDate(strdate);
        return formatDateByFormat(date, "yyyy-MM") + "-01";
    }

    /**
     * 以指定的格式来格式化日期
     *
     * @param date
     *            Date
     * @param format
     *            String
     * @return String
     */
    public static String formatDateByFormat(Date date, String format) {
        String result = "";
        if (date != null) {
            try {
                SimpleDateFormat sdf = new SimpleDateFormat(format);
                result = sdf.format(date);
            } catch (Exception ex) {
                ex.printStackTrace();
            }
        }
        return result;
    }

    /**
     * 常用的格式化日期
     * 默认格式yyyy-MM-dd
     * @param date
     *            Date
     * @return String
     */
    public static String formatDate(Date date) {
        return formatDateByFormat(date, "yyyy-MM-dd");
    }

    /**
     * @根据当前日期计算n天后的日期
     * @return String
     */
    public static Date afterNDay(Date date, int n) {
        Calendar c = Calendar.getInstance();
        c.setTime(date);
        c.add(Calendar.DATE, n);
        Date destDay = c.getTime();
        return destDay;
    }

    /**
     * 两个日期间的天数
     */
    public static int getIntervalDays(Date startday, Date endday) {
        if (startday.after(endday)) {
            Date cal = startday;
            startday = endday;
            endday = cal;
        }
        long sl = startday.getTime();
        long el = endday.getTime();
        long ei = el - sl;
        return (int) (ei / (1000 * 60 * 60 * 24));
    }

    public static boolean  verifyDate(String birthday){
        String [] array = birthday.split("-");
        if(null == array || array.length != 3 || array[0].length() !=4 || 
                        array[1].length() != 2 || array[2].length() != 2)
            return false;
        int curyear = DateUtil.getYear(new Date());
        try {
            int studyear = Integer.parseInt(array[0]);
            if(studyear <= 1900 || studyear > curyear)
                return false;
            String curDateStr = formatDateByFormat(new Date(), DATE_FORMAT);
            if(birthday.compareTo(curDateStr) >= 0)
                return false;
            return checkDate(birthday);
        } catch (NumberFormatException e) {
            return false;
        }
    }

    private static boolean checkDate(String date) {
        // System.out.println(date);
        // 判断年月日的正则表达式，接受输入格式为2010-12-24，可接受平年闰年的日期
        String regex = "(([0-9]{3}[1-9]|[0-9]{2}[1-9][0-9]{1}|[0-9]{1}[1-9][0-9]{2}
            |[1-9][0-9]{3})-(((0[13578]|1[02])-(0[1-9]|[12][0-9]|3[01]))|((0[469]|
            11)-(0[1-9]|[12][0-9]|30))|(02-(0[1-9]|[1][0-9]|2[0-8]))))|((([0-9]{2})
            (0[48]|[2468][048]|[13579][26])|((0[48]|[2468][048]|[3579][26])00))
             -02-29)";
        Pattern pattern = Pattern.compile(regex);
        Matcher matcherObj = pattern.matcher(date);
        return matcherObj.matches();
    }

    public static Date addMonths(Date date, int amount) {
        final SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");
        sdf.setLenient(false);
        String ymd=sdf.format(date);
        final Calendar calendar = new GregorianCalendar();
        calendar.setLenient(false);
        calendar.set(Integer.parseInt(ymd.substring(0, 4)),
                Integer.parseInt(ymd.substring(4, 6)),
                Integer.parseInt(ymd.substring(6)));
        calendar.add(Calendar.MONTH, amount);
        String newDate1=sdf.format(calendar.getTime())  ;
        Date newDate2=parseDate1(newDate1);
        return newDate2;
    }

    public static String stringToday() { return stringToday(null); }

    public static String stringToday(String separator) {
        String separatorValue = StringUtils.trimToEmpty(separator);
        Calendar calendar = Calendar.getInstance();

        return DateFormatUtils.format(calendar, "yyyy-MM-dd".replace("-", separatorValue));
    }

}