Java日期函数处理Util类

package main;

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

public class DateUtils
{
    /**
     * Number of milliseconds in a standard second.
     */
    public static final long MILLIS_PER_SECOND = 1000;// 一秒钟的毫秒数
    
    /**
     * Number of milliseconds in a standard minute.
     */
    public static final long MILLIS_PER_MINUTE = 60 * MILLIS_PER_SECOND;// 一分钟的毫秒数

    /**
     * Number of milliseconds in a standard hour.
     */
    public static final long MILLIS_PER_HOUR = 60 * MILLIS_PER_MINUTE;// 一小时的毫秒数

    /**
     * Number of milliseconds in a standard day.
     */
    public static final long MILLIS_PER_DAY = 24 * MILLIS_PER_HOUR;// 一天的毫秒数
    
    /**
     * ISO8601 date format: yyyy-MM-dd
     */
    public static final String DATE_FORMAT_PATTERN = "yyyy-MM-dd";

    /**
     * ISO8601 date-time format: yyyy-MM-dd HH:mm:ss
     */
    public static String DATETIME_FORMAT_PATTERN = "yyyy-MM-dd HH:mm:ss";
    
    private DateUtils()
    {
        
    }
    
    public static String fillZero(String str, int fillSize)
    {
        if (null != str)
        {
            int beforeSize = str.length();
            if(str.length() < fillSize)
            {
                int afterSize = fillSize-beforeSize;
                for(int i=0; i<afterSize; i++)
                {
                    str = "0"+str;
                }
            }
        }
        
        return str;
    }

    /**
     * 获得系统时间yyyy-MM-dd HH:mm:ss格式
     * 
     * @return
     */
    public static String getSystime() {
        Calendar todaysDate = new GregorianCalendar();
        int year = todaysDate.get(Calendar.YEAR);
        int month = todaysDate.get(Calendar.MONTH) + 1;
        int day = todaysDate.get(Calendar.DAY_OF_MONTH);
        int hourOfDay = todaysDate.get(Calendar.HOUR_OF_DAY);//24小时制
        // int hour = todaysDate.get(Calendar.HOUR); //12小时制
        int minute = todaysDate.get(Calendar.MINUTE);
        int second = todaysDate.get(Calendar.SECOND);
        
        return year + "/" + month + "/" + day + " " + hourOfDay + ":" + fillZero(minute+"", 2)
                + ":" + fillZero(second+"", 2);
    }
    /**
     * 获得当前时间yyyy-MM-dd HH:mm:ss格式
     * @return
     */
    public static String getCurrentDateAsString()
    {
        SimpleDateFormat formatter = new SimpleDateFormat(DATETIME_FORMAT_PATTERN);

        return formatter.format(new Date());
    }
    /**
     * 获得当前日期yyyy-MM-dd HH:mm:ss格式
     * @return
     */
    public static Date getCurrentDate()
    {
        return parseToDate(getCurrentDateAsString(), DATETIME_FORMAT_PATTERN);
    }
    
    /**
     * 将日期字符串转换为指定的日期格式
     * 
     * @param str 日期字符串
     * @param pattern 日期格式
     * @return
     */
    public static Date parseToDate(String str, String pattern)
    {
        DateFormat parser = new SimpleDateFormat(pattern);
        try
        {
            return parser.parse(str);
        }
        catch (ParseException e)
        {
            throw new IllegalArgumentException("Can't parse " + str + " using " + pattern);
        }
    }
    /**
     * 将yyyy-MM-dd HH:mm:ss格式字符串转成Date
     * @param str
     * @return
     */
    public static Date parseToDate(String str)
    {
        return parseToDate(str, DATETIME_FORMAT_PATTERN);
    }
    
    /**
     * 比较两个时间数相差多少分钟
     * @param begin
     * @param end
     * @return
     */
    public static long getDiff(Date begin, Date end)
    {
        long diff = end.getTime() - begin.getTime();
        diff = Math.abs(diff);
        
        long day = diff / MILLIS_PER_DAY;// 计算差多少天
        long hour = diff % MILLIS_PER_DAY / MILLIS_PER_HOUR;// 计算差多少小时
        long min = diff % MILLIS_PER_DAY % MILLIS_PER_HOUR / MILLIS_PER_MINUTE;// 计算差多少分钟
        long sec = diff % MILLIS_PER_DAY % MILLIS_PER_HOUR % MILLIS_PER_MINUTE / MILLIS_PER_SECOND;// 计算差多少秒
        
        System.out.println("时间相差：" + day + "天" + hour + "小时" + min + "分钟" + sec + "秒。");
        
        return min;
    }
    
    /**
     * 获得指定日期的前一天
     * 
     * @param specifiedDay yy-MM-dd
     * @return
     * @throws Exception
     */
    public static String getBeforeDay(String specifiedDay)
    {
        Calendar c = Calendar.getInstance();
        Date date = null;
        try
        {
            date = new SimpleDateFormat(DATE_FORMAT_PATTERN).parse(specifiedDay);
        }
        catch (ParseException e)
        {
            e.printStackTrace();
        }
        c.setTime(date);
        int day = c.get(Calendar.DATE);
        c.set(Calendar.DATE, day - 1);

        String dayBefore = new SimpleDateFormat(DATE_FORMAT_PATTERN).format(c.getTime());
        return dayBefore;
    }

    /**
     * 获得指定日期的后一天
     * 
     * @param specifiedDay yy-MM-dd
     * @return
     */
    public static String getAfterDay(String specifiedDay)
    {
        Calendar c = Calendar.getInstance();
        Date date = null;
        try
        {
            date = new SimpleDateFormat(DATE_FORMAT_PATTERN).parse(specifiedDay);
        }
        catch (ParseException e)
        {
            e.printStackTrace();
        }
        c.setTime(date);
        int day = c.get(Calendar.DATE);
        c.set(Calendar.DATE, day + 1);

        String dayAfter = new SimpleDateFormat(DATE_FORMAT_PATTERN).format(c.getTime());
        return dayAfter;
    }

    /** 
     * 获得一个月的最后一天
     * @param date null|当天
     * @return Date
     */  
    public static Date getLastDayOfMonth(Date date) {  
        // 获取Calendar
        Calendar calendar = Calendar.getInstance();
        // 设置时间,当前时间不用设置(NULL当天)
        if(date != null)
            calendar.setTime(date);
  
        calendar.set(Calendar.DATE, calendar.getMaximum(Calendar.DATE));
        
        DateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");  
        System.out.println(format.format(calendar.getTime()));
        
        return calendar.getTime();  
    }     

    /**  
     * 计算两个日期之间相差的天数  
     * @param d1 较小的时间 
     * @param d2  较大的时间 
     * @return 相差天数 
     * @throws ParseException  
     */    
    public static int daysBetween(Date d1, Date d2) throws ParseException
    {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        d1 = sdf.parse(sdf.format(d1));
        d2 = sdf.parse(sdf.format(d2));
        
        Calendar cal = Calendar.getInstance();
        cal.setTime(d1);
        long time1 = cal.getTimeInMillis();
        cal.setTime(d2);
        long time2 = cal.getTimeInMillis();
        long betweenDays = (time2 - time1) / (1000 * 3600 * 24);
        return Integer.parseInt(String.valueOf(betweenDays));
    }
    /**
     * 获得两个时间之间隔的天数
     * 
     * @return
     */
    public static int daysBetween(String d1, String d2) throws ParseException
    {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        Calendar cal = Calendar.getInstance();
        cal.setTime(sdf.parse(d1));
        long time1 = cal.getTimeInMillis();
        cal.setTime(sdf.parse(d2));
        long time2 = cal.getTimeInMillis();
        long betweenDays = (time2 - time1) / (1000 * 3600 * 24);
        
        return Integer.parseInt(String.valueOf(betweenDays));
    }
    /**
     * 计算两个日期之间相差的月数
     * 
     * @param date1
     * @param date2
     * @return
     */
    public static int getMonth(Date date1, Date date2) {
        int iMonth = 0;
        int flag = 0;
        try {
            Calendar cal1 = Calendar.getInstance();
            cal1.setTime(date1);

            Calendar cal2 = Calendar.getInstance();
            cal2.setTime(date2);

            if (cal2.equals(cal1)) return 0;
            if (cal1.after(cal2)) {
                Calendar temp = cal1;
                cal1 = cal2;
                cal2 = temp;
            }
            if (cal2.get(Calendar.DAY_OF_MONTH) < cal1.get(Calendar.DAY_OF_MONTH)) flag = 1;

            if (cal2.get(Calendar.YEAR) > cal1.get(Calendar.YEAR))
                iMonth = ((cal2.get(Calendar.YEAR) - cal1.get(Calendar.YEAR)) * 12 + cal2.get(Calendar.MONTH) - flag)
                         - cal1.get(Calendar.MONTH);
            else iMonth = cal2.get(Calendar.MONTH) - cal1.get(Calendar.MONTH) - flag;

        } catch (Exception e) {
            e.printStackTrace();
        }
        return iMonth;
    }
}