时间格式转化与计算代码（java）

*
* <p>Title: 时间格式转化与计算</p>
*/

package web.com;

import java.util.Calendar;
import java.util.Date;
import java.text.*;

public class DateTime {
   public DateTime() {
   }

   /**
    * 取得系统当前时间
    * @return String yyyy-mm-dd
    */
   public String getCurrentDate() {
     Calendar rightNow = Calendar.getInstance();
     int year = rightNow.get(rightNow.YEAR);
     int month = rightNow.get(rightNow.MONTH) + 1;
     int day = rightNow.get(rightNow.DATE);
     return year + "-" + month + "-" + day;
   }

   /**
    * 取得系统当前时间
    * @return String yyyy年mm月dd日
    */
   public String getCurrentDate1() {
     Calendar rightNow = Calendar.getInstance();
     int year = rightNow.get(rightNow.YEAR);
     int month = rightNow.get(rightNow.MONTH) + 1;
     int day = rightNow.get(rightNow.DATE);
     return year + "年" + month + "月" + day + "日";
   }

   /**
    * 取得系统当前时间
    * @return String yyyymmdd
    */
   public String getCurrentDate2() {
     Calendar rightNow = Calendar.getInstance();
     int year = rightNow.get(rightNow.YEAR);
     int month = rightNow.get(rightNow.MONTH) + 1;
     int day = rightNow.get(rightNow.DATE);
     return year + "" + month + "" + day;
   }

   /**
    * 取得系统当前时间
    * @return String yyyy-mm
    */
   public String getCurrentDate3() {
     Calendar rightNow = Calendar.getInstance();
     int year = rightNow.get(rightNow.YEAR);
     int month = rightNow.get(rightNow.MONTH) + 1;
     //int day = rightNow.get(rightNow.DATE);
     return year + "-" + month;
   }

   /**
    * 取得系统当前时间
    * @return String yyyyMMddhhmmss
    */
   public String getCurrentDate4() {
      Calendar c = Calendar.getInstance();
          c.add(c.SECOND, 0);

          return "" + c.get(c.YEAR) + "" + (c.get(c.MONTH) + 1) + "" + c.get(c.DATE)+""+c.get(c.HOUR_OF_DAY)+""+c.get(c.MINUTE)+""+c.get(c.SECOND);

}

   /**
    * 取得系统当前时间
    * @return String yyyy-MM-dd hh:mm:ss
    */
/* public String getCurrentDate5() {
     SimpleDateFormat simpleDateFormat =new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
     java.util.Date date = new java.util.Date();
     String time = simpleDateFormat.format(date);
     return time;
   }
*/
/**
* 取得系统当前时间
* @return String yyyy-MM-dd hh:mm:ss
*/

     public String getCurrentDate5(){
         Calendar c = Calendar.getInstance();
         c.add(c.SECOND, 0);
         return "" + c.get(c.YEAR) + "-" + (c.get(c.MONTH) + 1) + "-" + c.get(c.DATE)+" "+c.get(c.HOUR_OF_DAY)+":"+c.get(c.MINUTE)+":"+c.get(c.SECOND);
       }

       /**
        * 取得系统当前时间 常用于订单号
        * @return String yyyyMMddhhmmss
        */
       public String getCurrentDate6() {
          Calendar c = Calendar.getInstance();
              c.add(c.SECOND, 0);
              String year=c.get(c.YEAR)+"";
              return "" + year.subSequence(2,year.length())+ "" + (c.get(c.MONTH) + 1) + "" + c.get(c.DATE)+"-"+c.get(c.HOUR_OF_DAY)+""+c.get(c.MINUTE)+""+c.get(c.SECOND)+"-"+c.get(c.MILLISECOND);

     }


   /**
    * 取得系统当前时间前n个月的相对应的一天
    * @param n int
    * @return String yyyy-mm-dd
    */
   public String getNMonthBeforeCurrentDay(int n) {
     Calendar c = Calendar.getInstance();
     c.add(c.MONTH, -n);
     return "" + c.get(c.YEAR) + "-" + (c.get(c.MONTH) + 1) + "-" + c.get(c.DATE);

   }

   /**
    * 取得系统当前时间后n个月的相对应的一天
    * @param n int
    * @return String   yyyy-mm-dd
    */
   public String getNMonthAfterCurrentDay(int n) {
     Calendar c = Calendar.getInstance();
     c.add(c.MONTH, n);
     return "" + c.get(c.YEAR) + "-" + (c.get(c.MONTH) + 1) + "-" + c.get(c.DATE);

   }

   /**
    * 取得系统当前时间前n天
    * @param n int
    * @return String yyyy-mm-dd
    */
   public String getNDayBeforeCurrentDate(int n) {
     Calendar c = Calendar.getInstance();
     c.add(c.DAY_OF_MONTH, -n);
     return "" + c.get(c.YEAR) + "-" + (c.get(c.MONTH) + 1) + "-" + c.get(c.DATE);
   }

   /**
    * 取得系统当前时间后n天
    * @param n int
    * @return String yyyy-mm-dd
    */
   public String getNDayAfterCurrentDate(int n) {
     Calendar c = Calendar.getInstance();
     c.add(c.DAY_OF_MONTH, n);
     return "" + c.get(c.YEAR) + "-" + (c.get(c.MONTH) + 1) + "-" + c.get(c.DATE);
   }

   //---------------------------------------------------------------------
   //取过去一个时间对应的系统当年的一天
   public String getCurrentDateAfterPastDate(String sPastDate) {
     if (sPastDate != null && !sPastDate.equals("")) {
       Date date = switchStringToDate(sPastDate);
       Calendar c = Calendar.getInstance();
       c.setTime(date);
       int iPastYear = c.get(c.YEAR);
       Calendar c1 = Calendar.getInstance();
       int iCurrentYear = c1.get(c1.YEAR);
       c.add(c.YEAR, iCurrentYear - iPastYear);
       return "" + c.get(c.YEAR) + "-" + (c.get(c.MONTH) + 1) + "-" +
           c.get(c.DATE);
     }
     else {
       return null;
     }
   }

   /**
    * 将一个日期字符串转化成日期
    * @param sDate String
    * @return Date yyyy-mm-dd
    */
   public Date switchStringToDate(String sDate) {
     Date date = null;
     try {
       SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
       date = df.parse(sDate);

     }
     catch (Exception e) {
       System.out.println("日期转换失败:" + e.getMessage());
     }
     return date;
   }

   /**
    * 输入两个字符串型的日期，比较两者的大小
    * @param fromDate String
    * @param toDate String
    * @return boolean before为true
    */
   public boolean compareTwoDateBigOrSmall(String fromDate, String toDate) {
     Date dateFrom = this.switchStringToDate(fromDate);
     Date dateTo = this.switchStringToDate(toDate);
     if (dateFrom.before(dateTo)) {
       return true;
     }
     else {
       return false;
     }
   }

   /**
    * 将一个日期字符串转化成Calendar
    * @param sDate String
    * @return Calendar
    */
   public Calendar switchStringToCalendar(String sDate) {
     Date date = switchStringToDate(sDate);
     Calendar c = Calendar.getInstance();
     c.setTime(date);
     return c;
   }

   /**
    * 将一个日期转化成Calendar
    * @param date Date
    * @return Calendar
    */
   public Calendar switchStringToCalendar(Date date) {
     Calendar c = Calendar.getInstance();
     c.setTime(date);
     return c;
   }

   public   String string2Date(String dateString)
   throws java.lang.Exception {
     /*DateFormat dateFormat;
     dateFormat = new SimpleDateFormat("yyyy-MM-dd kk:mm:ss");
     dateFormat.setLenient(false);
     java.util.Date timeDate = dateFormat.parse(dateString);//util类型
     //java.sql.Date dateTime = new java.sql.Date(timeDate.getTime());//sql类型
     java.sql.Timestamp dateTime = new java.sql.Timestamp(timeDate.getTime());//Timestamp类型
     */
     SimpleDateFormat newk = new SimpleDateFormat ("yyyy.MM.dd hh:mm:ss");
    SimpleDateFormat old = new SimpleDateFormat("MMM dd hh:mm:ss yyyy");

    String strDate = "Mar 22 00:42:00 2002";
    Date d = old.parse(strDate);
    System.out.println(newk.format(d));

     return newk.format(d);
   }



   /**
    * 取得某个时间前n个月的相对应的一天
    * @param sDate String
    * @param n int
    * @return String yyyy-mm-dd
    */
   public String getNMonthBeforeOneDay(String sDate, int n) {
     Calendar c = switchStringToCalendar(sDate);
     c.add(c.MONTH, -n);
     return "" + c.get(c.YEAR) + "-" + (c.get(c.MONTH) + 1) + "-" + c.get(c.DATE);

   }

   //取得某个时间后n个月的相对应的一天
   public String getNMonthAfterOneDay(String sDate, int n) {
     Calendar c = switchStringToCalendar(sDate);
     c.add(c.MONTH, n);
     return "" + c.get(c.YEAR) + "-" + (c.get(c.MONTH) + 1) + "-" + c.get(c.DATE);

   }

   //取得某个时间前n天,格式为yyyy-mm-dd
   public String getNDayBeforeOneDate(String sDate, int n) {
     Calendar c = switchStringToCalendar(sDate);
     c.add(c.DAY_OF_MONTH, -n);
     return "" + c.get(c.YEAR) + "-" + (c.get(c.MONTH) + 1) + "-" + c.get(c.DATE);
   }

   //取得某个时间后n天,格式为yyyy-mm-dd
   public String getNDayAfterOneDate(String sDate, int n) {
     Calendar c = switchStringToCalendar(sDate);
     c.add(c.DAY_OF_MONTH, n);
     return "" + c.get(c.YEAR) + "-" + (c.get(c.MONTH) + 1) + "-" + c.get(c.DATE);
   }

   //判断系统当前时间是不是润年
   public boolean isRunNian() {
     java.util.Calendar rightNow = java.util.Calendar.getInstance();
     int year = rightNow.get(rightNow.YEAR);
     if (0 == year % 4 && (year % 100 != 0 || year % 400 == 0)) {
       return true;
     }
     else {
       return false;
     }

   }

   public static void main(String args[]) {
     DateTime a = new DateTime();
     try{
       System.out.println(a.getCurrentDate6());
       System.out.println(a.getCurrentDate6());
     }catch(Exception e){System.err.println();}

   }