java处理日期时间的方法

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.*;

public class DateUtils {
    public static void main(String[] args) throws ParseException {
        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
        String str = "2012-05-02";
        Date date = df.parse(str);
        Map<String, String> map = getFirstday_Lastday_Month(date);
        System.out.println("当月第一天：" + getFirstDay());//两种方式getFirstDay()，getFirstDay1()
        System.out.println("当月最后一天：" + getLastDay());//同
        System.out.println("月最后一天：" + getLastDay());//同

        System.out.println("一个月前第一天：" + map.get("first"));
        System.out.println("一个月前最后一天：" + map.get("last"));

        System.out.println("获取前一个月的第一天：" + getPreMonthFirstDay());
        System.out.println("获取前一个月的最后一天：" +getPreMonthLastDay());

        Calendar calendar = new GregorianCalendar();
        calendar.setTime(date); //放入你的日期
        System.out.println("天数为=" + calendar.getActualMaximum(Calendar.DAY_OF_MONTH));
    }

    /**
     * 计算两个日期相差的月份数
     *
     * @param date1   日期1
     * @param date2   日期2
     * @param pattern 日期1和日期2的日期格式
     * @return 相差的月份数
     * @throws ParseException
     */
    public static int countMonths(String date1, String date2, String pattern) throws ParseException {
        SimpleDateFormat sdf = new SimpleDateFormat(pattern);

        Calendar c1 = Calendar.getInstance();
        Calendar c2 = Calendar.getInstance();

        c1.setTime(sdf.parse(date1));
        c2.setTime(sdf.parse(date2));


        int year = c2.get(Calendar.YEAR) - c1.get(Calendar.YEAR);

        //开始日期若小于结束日期
        if (year < 0) {
            year = -year;
            return year * 12 + c1.get(Calendar.MONTH) - c2.get(Calendar.MONTH);
        }

        return year * 12 + c2.get(Calendar.MONTH) - c1.get(Calendar.MONTH) + 1;
    }




   //获取当前月第一天：方式一
    private static String getFirstDay() {
        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
        Calendar calendar = Calendar.getInstance();
        Date theDate = calendar.getTime();

        GregorianCalendar gcLast = (GregorianCalendar) Calendar.getInstance();
        gcLast.setTime(theDate);
        gcLast.set(Calendar.DAY_OF_MONTH, 1);
        String day_first = df.format(gcLast.getTime());
        StringBuffer str = new StringBuffer().append(day_first).append(" 00:00:00");
        return str.toString();
    }

    //获取当前月第一天：方式二
    private static String getFirstDay1() {
        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
        Calendar c = Calendar.getInstance();
        c.add(Calendar.MONTH, 0);
        c.set(Calendar.DAY_OF_MONTH, 1);//设置为1号,当前日期既为本月第一天
        String first_Day_Of_Month = df.format(c.getTime());
        return first_Day_Of_Month;
    }


    //获取当月最后一天:方式一
    private static String getLastDay() {
        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
        Calendar calendar = Calendar.getInstance();
        Date theDate = calendar.getTime();
        String s = df.format(theDate);
        StringBuffer str = new StringBuffer().append(s).append(" 23:59:59");
        return str.toString();

    }

    //获取当前月最后一天:方式二
    private static String getLastDay1() {
        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
        Calendar ca = Calendar.getInstance();
        ca.set(Calendar.DAY_OF_MONTH, ca.getActualMaximum(Calendar.DAY_OF_MONTH));
        String lastDay = df.format(ca.getTime());
        return lastDay;
    }

    //获取前月的第一天
    private static String getPreMonthFirstDay() {
        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
        Calendar cal_1 = Calendar.getInstance();//获取当前日期
        cal_1.add(Calendar.MONTH, -1);
        cal_1.set(Calendar.DAY_OF_MONTH, 1);//设置为1号,当前日期既为本月第一天
        String firstDay = df.format(cal_1.getTime());
        return firstDay;
    }

    //获取前月的最后一天
    private static String getPreMonthLastDay() {
        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
        Calendar cale = Calendar.getInstance();
        cale.set(Calendar.DAY_OF_MONTH, 0);//设置为1号,当前日期既为本月第一天
        String lastDay = df.format(cale.getTime());
        System.out.println("-----2------lastDay:" + lastDay);
        return lastDay;
    }
    /**
     * 某一个月第一天和最后一天
     */
    private static Map<String, String> getFirstday_Lastday_Month(Date date) {
        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        calendar.add(Calendar.MONTH, -1);
        Date theDate = calendar.getTime();

        //上个月第一天
        GregorianCalendar gcLast = (GregorianCalendar) Calendar.getInstance();
        gcLast.setTime(theDate);
        gcLast.set(Calendar.DAY_OF_MONTH, 1);
        String day_first = df.format(gcLast.getTime());
        StringBuffer str = new StringBuffer().append(day_first).append(" 00:00:00");
        day_first = str.toString();

        //上个月最后一天
        calendar.add(Calendar.MONTH, 1);    //加一个月
        calendar.set(Calendar.DATE, 1);        //设置为该月第一天
        calendar.add(Calendar.DATE, -1);    //再减一天即为上个月最后一天
        String day_last = df.format(calendar.getTime());
        StringBuffer endStr = new StringBuffer().append(day_last).append(" 23:59:59");
        day_last = endStr.toString();

        Map<String, String> map = new HashMap<String, String>();
        map.put("first", day_first);
        map.put("last", day_last);
        return map;
    }


    public static List<String> getMonthBetween(String minDate, String maxDate) throws ParseException {
        ArrayList<String> result = new ArrayList<String>();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM");//格式化为年月

        Calendar min = Calendar.getInstance();
        Calendar max = Calendar.getInstance();

        min.setTime(sdf.parse(minDate));
        min.set(min.get(Calendar.YEAR), min.get(Calendar.MONTH), 1);

        max.setTime(sdf.parse(maxDate));
        max.set(max.get(Calendar.YEAR), max.get(Calendar.MONTH), 2);

        Calendar curr = min;
        while (curr.before(max)) {
            result.add(sdf.format(curr.getTime()));
            curr.add(Calendar.MONTH, 1);
        }

        return result;
    }

    //获取某一日期的哪一天
    public static int getDayOfMonth(String nowDate) {
        Calendar c = Calendar.getInstance();//获得一个日历的实例
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        Date date = null;
        try {
            date = sdf.parse(nowDate);//初始日期
        } catch (Exception e) {

        }
        c.setTime(date);//设置日历时间
        return c.get(Calendar.DAY_OF_MONTH);
    }

    public static String dateFormatToString(Date date, String formatString) {
        java.text.SimpleDateFormat formatter = new SimpleDateFormat(formatString);

        return formatter.format(date);//格式化数据
    }

    public static Date dateFormatToDate(String date) throws ParseException {
        java.text.SimpleDateFormat formatter =  new SimpleDateFormat("yyyy-MM-dd ");
        return formatter.parse(date);
    }

    public static int compare_date(String nowDATE, String endDATE) {
        DateFormat df = new SimpleDateFormat("yyyy-MM-dd");
        try {
            Date dt1 = df.parse(nowDATE);
            Date dt2 = df.parse(endDATE);
            if (dt1.getTime() > dt2.getTime()) {
                //System.out.println("dt1 在dt2前");
                return 1;
            } else if (dt1.getTime() < dt2.getTime()) {
                //System.out.println("dt1在dt2后");
                return -1;
            } else {
                return 0;
            }
        } catch (Exception exception) {
            exception.printStackTrace();
        }
        return 0;
    }

   
    public static int getMonthToDay(String date) throws ParseException {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        Calendar calendar = new GregorianCalendar();
        Date date1 = sdf.parse(date);
        calendar.setTime(date1); //放入你的日期
        return calendar.getActualMaximum(Calendar.DAY_OF_MONTH);
    }


    //获取当前时间的年和月：
    public int getCurrentYearAndMonth() throws ParseException {
        SimpleDateFormat formatter = new SimpleDateFormat("yyyyMM");
        Date date = new Date();
        String currentYearAndMonth = formatter.format(date);
        int currentDate = Integer.parseInt(currentYearAndMonth);
        return currentDate;
    }

//======================================比较两个日期相差的天数 ================================================
    //（版本1）：根据您输入的小时与分不同，返回不同的结果的，
    // 比如你输入的参数今天中午与昨天晚上的两个时间，它就会告诉你相差0天
    public static int getIntervalDays(Date fDate, Date oDate) {
        if (null == fDate || null == oDate) {
            return -1;
        }
        long intervalMilli = oDate.getTime() - fDate.getTime();
        return (int) (intervalMilli / (24 * 60 * 60 * 1000));
    }

    //（版本2）
    public static int daysBetween(Date smdate,Date bdate) throws ParseException{
        SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");
        smdate=sdf.parse(sdf.format(smdate));
        bdate=sdf.parse(sdf.format(bdate));
        Calendar cal = Calendar.getInstance();
        cal.setTime(smdate);
        long time1 = cal.getTimeInMillis();
        cal.setTime(bdate);
        long time2 = cal.getTimeInMillis();
        long between_days=(time2-time1)/(1000*3600*24);
        return Integer.parseInt(String.valueOf(between_days));
    }

    //（版本3）：你输入的参数今天中午与昨天晚上的两个时间，只关心天，因此输出的结果是1
    public static int daysOfTwo(Date fDate, Date oDate) {
        Calendar aCalendar = Calendar.getInstance();
        aCalendar.setTime(fDate);
        int day1 = aCalendar.get(Calendar.DAY_OF_YEAR);
        aCalendar.setTime(oDate);
        int day2 = aCalendar.get(Calendar.DAY_OF_YEAR);
        return day2 - day1;
    }
//======================================================================================
}

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