日期按、天、月、季度计算及格式化

最近开发的项目平凡用到时间的各种计算及转化，虽然没多少技术含量但也记录一下。
直接上代码拿走不谢。

import org.apache.http.client.utils.DateUtils;

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

public class DateUtil {
    /**
     * 获取系统你天前或n天后的日期
     * @param days
     * @return
     */
    public static String daysAgo(int days){
        Calendar calendar1 = Calendar.getInstance();
        SimpleDateFormat sdf1 = new SimpleDateFormat("yyyy-MM-dd 00:00:00");
        calendar1.add(Calendar.DATE, days);
        String days_ago = sdf1.format(calendar1.getTime());
        return days_ago;
    }

    /**
     * 时间戳转换成日期格式字符串
     * @param seconds 精确到秒的字符串

     * @return
     */
    public static String timeStamp2Date(String seconds,String format) {
        if(seconds == null || seconds.isEmpty() || seconds.equals("null")){
            return "";
        }
        if(format == null || format.isEmpty()){
            format = "yyyy-MM-dd HH:mm:ss";
        }
        SimpleDateFormat sdf = new SimpleDateFormat(format);
        return sdf.format(new Date(Long.valueOf(seconds+"000")));
    }
    /**
     * 日期格式字符串转换成时间戳

     * @param format 如：yyyy-MM-dd HH:mm:ss
     * @return
     */
    public static String date2TimeStamp(String date_str,String format){
        try {
            SimpleDateFormat sdf = new SimpleDateFormat(format);
            return String.valueOf(sdf.parse(date_str).getTime()/1000);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return "";
    }

    /**
     * 取得当前时间戳（精确到秒）
     * @return
     */
    public static String timeStamp(){
        long time = System.currentTimeMillis();
        String t = String.valueOf(time/1000);
        return t;
    }


    /**
     * 获取两个日期相差的天数
     *
     * @param startDateStr 开始时间
     * @param endDateStr 结束时间
     */
    public static int getDayBetweenTwoDate(String startDateStr, String endDateStr) {
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
        int days = 0;
        try {
            Date startDate = simpleDateFormat.parse(startDateStr);
            Date endDate = simpleDateFormat.parse(endDateStr);
            Calendar startCalendar = Calendar.getInstance();
            startCalendar.setTime(startDate);
            Calendar endCalendar = Calendar.getInstance();
            endCalendar.setTime(endDate);
            //计算两个日期相差的天数
            //startCalendar.getTime().getTime()返回long毫秒数形式,毫秒转为秒所以除以1000
            //1天=24小时，1小时=60分，1分=60秒，所以两个时间的差再除以60 * 60 * 24换算成天的形式
            days = ((int) (startCalendar.getTime().getTime() / 1000) - (int) (endCalendar.getTime().getTime() / 1000)) / (60 * 60 * 24);

        } catch (ParseException e) {
            e.printStackTrace();
        }
        return days;
    }

    /**
     * 某一个月第一天和最后一天
     *
     * @param date 指定日期
     * @param pattern 日期格式
     * @param isNeedHms 是否需要时分秒
     * @return
     */
    public static Map<String, Object> getFirstLastDayByMonth(Date date,
                                                             String pattern, boolean isNeedHms) {
        SimpleDateFormat df = new SimpleDateFormat(pattern);
        Calendar calendar = Calendar.getInstance();

        calendar.setTime(date);
        Date theDate = calendar.getTime();

        // 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);
        if (isNeedHms)
            str.append(" 00:00:00");
        day_first = str.toString();

        // 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);
        if (isNeedHms)
            endStr.append(" 23:59:59");
        day_last = endStr.toString();

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



    /**
     * 获取当前季度
     *
     */
    public static String getQuarter() {
        Calendar c = Calendar.getInstance();
        int month = c.get(c.MONTH) + 1;
        int quarter = 0;
        if (month >= 1 && month <= 3) {
            quarter = 1;
        } else if (month >= 4 && month <= 6) {
            quarter = 2;
        } else if (month >= 7 && month <= 9) {
            quarter = 3;
        } else {
            quarter = 4;
        }
        return quarter + "";
    }

    /**
     * 获取某季度的第一天和最后一天
     *	@param num 第几季度
     */
    public static String[] getCurrQuarter(int num) {
        String[] s = new String[2];
        String str = "";
        // 设置本年的季
        Calendar quarterCalendar = null;
        switch (num) {
            case 1: // 本年到现在经过了一个季度，在加上前4个季度
                quarterCalendar = Calendar.getInstance();
                quarterCalendar.set(Calendar.MONTH, 3);
                quarterCalendar.set(Calendar.DATE, 1);
                quarterCalendar.add(Calendar.DATE, -1);
                str = DateUtils.formatDate(quarterCalendar.getTime(), "yyyy-MM-dd");
                s[0] = str.substring(0, str.length() - 5) + "01-01";
                s[1] = str;
                break;
            case 2: // 本年到现在经过了二个季度，在加上前三个季度
                quarterCalendar = Calendar.getInstance();
                quarterCalendar.set(Calendar.MONTH, 6);
                quarterCalendar.set(Calendar.DATE, 1);
                quarterCalendar.add(Calendar.DATE, -1);
                str = DateUtils.formatDate(quarterCalendar.getTime(), "yyyy-MM-dd");
                s[0] = str.substring(0, str.length() - 5) + "04-01";
                s[1] = str;
                break;
            case 3:// 本年到现在经过了三个季度，在加上前二个季度
                quarterCalendar = Calendar.getInstance();
                quarterCalendar.set(Calendar.MONTH, 9);
                quarterCalendar.set(Calendar.DATE, 1);
                quarterCalendar.add(Calendar.DATE, -1);
                str = DateUtils.formatDate(quarterCalendar.getTime(), "yyyy-MM-dd");
                s[0] = str.substring(0, str.length() - 5) + "07-01";
                s[1] = str;
                break;
            case 4:// 本年到现在经过了四个季度，在加上前一个季度
                quarterCalendar = Calendar.getInstance();
                str = DateUtils.formatDate(quarterCalendar.getTime(), "yyyy-MM-dd");
                s[0] = str.substring(0, str.length() - 5) + "10-01";
                s[1] = str.substring(0, str.length() - 5) + "12-31";
                break;
        }
        return s;
    }


    /**
     * 根据日期（Date）获取哪年的第几季度
     * @param date
     * @return
     * @throws ParseException
     */
    public static String GetQuarterByDate(String date) throws ParseException{
        if(date == ""|| "".equals(date)){
            return "";
        }
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        Date datePar = sdf.parse(date);
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(datePar);

        //String year = String.valueOf(calendar.get(Calendar.YEAR));
        int mouth = datePar.getMonth();

        if(mouth>=1 && mouth<=3){
            return "1"; //"第一季度";
        }else if(mouth>=4 && mouth<=6){
            return "2"; //"第二季度";
        }else if(mouth>=7 && mouth<=9){
            return "3"; //"第三季度";
        }else if(mouth>=10 && mouth<=12){
            return "4"; //"第四季度";
        }else{
            return "";
        }
    }

   
    /**
     * 用途：以指定的格式格式化日期字符串
     * @param pattern 字符串的格式
     * @param currentDate 被格式化日期
     * @return String 已格式化的日期字符串
     * @throws NullPointerException 如果参数为空
     */
    public static String formatDate(Date currentDate, String pattern){
        if(currentDate == null || "".equals(pattern) || pattern == null){
            return null;
        }
        SimpleDateFormat sdf = new SimpleDateFormat(pattern);
        return sdf.format(currentDate);
    }

    /**
     *
     * @param time 时间
     * @param num 加的数，-num就是减去
     * @return 减去相应的数量的月份的日期
     * @throws ParseException Date
     */
    public static Date monthAddNum(Date time, Integer num){
        //SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        //Date date = format.parse(time);

        Calendar calendar = Calendar.getInstance();
        calendar.setTime(time);
        calendar.add(Calendar.MONTH, num);
        Date newTime = calendar.getTime();
        return newTime;
    }




    public static void main(String[] args) {

    }


}