1.string格式转化为Date对象：

//把string转化为date
DateFormat fmt =new SimpleDateFormat("yyyy-MM-dd");
Date date = fmt.parse(szBeginTime);
test.setStartTime(date);

注意：引入的是：java.text.DateFormat

2.Date格式转化为String对象：

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
String startTime = sdf.format(startTime);

Java时间格式转换大全


import java.text.*;
import java.util.Calendar;
public class VeDate {

public static Date getNowDate() {
   Date currentTime = new Date();
   SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
   String dateString = formatter.format(currentTime);
   ParsePosition pos = new ParsePosition(8);
   Date currentTime_2 = formatter.parse(dateString, pos);
   return currentTime_2;
}

DateFormat format1 = new SimpleDateFormat("yyyy-MM-dd");         
DateFormat format 2= new SimpleDateFormat("yyyy年MM月dd日 HH时mm分ss秒");         
Date date = null;    
String str = null;                  
            
// String转Date    
str = "2007-1-18";          
try {    
           date = format1.parse(str);   
           data = format2.parse(str); 
} catch (ParseException e) {    
           e.printStackTrace();    
}   

public static String getStringDate() {
   Date currentTime = new Date();
   SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
   String dateString = formatter.format(currentTime);
   return dateString;
}

public static String getStringDateShort() {
   Date currentTime = new Date();
   SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
   String dateString = formatter.format(currentTime);
   return dateString;
}

public static String getTimeShort() {
   SimpleDateFormat formatter = new SimpleDateFormat("HH:mm:ss");
   Date currentTime = new Date();
   String dateString = formatter.format(currentTime);
   return dateString;
}

public static Date strToDateLong(String strDate) {
   SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
   ParsePosition pos = new ParsePosition(0);
   Date strtodate = formatter.parse(strDate, pos);
   return strtodate;
}

public static String dateToStrLong(java.util.Date dateDate) {
   SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
   String dateString = formatter.format(dateDate);
   return dateString;
}

public static String dateToStr(java.util.Date dateDate) {
   SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
   String dateString = formatter.format(dateDate);
   return dateString;
}

public static Date strToDate(String strDate) {
   SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
   ParsePosition pos = new ParsePosition(0);
   Date strtodate = formatter.parse(strDate, pos);
   return strtodate;
}

public static Date getNow() {
   Date currentTime = new Date();
   return currentTime;
}

public static Date getLastDate(long day) {
   Date date = new Date();
   long date_3_hm = date.getTime() - 3600000 * 34 * day;
   Date date_3_hm_date = new Date(date_3_hm);
   return date_3_hm_date;
}

public static String getStringToday() {
   Date currentTime = new Date();
   SimpleDateFormat formatter = new SimpleDateFormat("yyyyMMdd HHmmss");
   String dateString = formatter.format(currentTime);
   return dateString;
}

public static String getHour() {
   Date currentTime = new Date();
   SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
   String dateString = formatter.format(currentTime);
   String hour;
   hour = dateString.substring(11, 13);
   return hour;
}

public static String getTime() {
   Date currentTime = new Date();
   SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
   String dateString = formatter.format(currentTime);
   String min;
   min = dateString.substring(14, 16);
   return min;
}

public static String getUserDate(String sformat) {
   Date currentTime = new Date();
   SimpleDateFormat formatter = new SimpleDateFormat(sformat);
   String dateString = formatter.format(currentTime);
   return dateString;
}--------------------------------------------------------------------------------------------------------------------------------


做成方法


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


public class VeDate {
 
 public static Date getNowDate() {
  Date currentTime = new Date();
  SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
  String dateString = formatter.format(currentTime);
  ParsePosition pos = new ParsePosition(8);
  Date currentTime_2 = formatter.parse(dateString, pos);
  return currentTime_2;
 }


 
 public static Date getNowDateShort() {
  Date currentTime = new Date();
  SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
  String dateString = formatter.format(currentTime);
  ParsePosition pos = new ParsePosition(8);
  Date currentTime_2 = formatter.parse(dateString, pos);
  return currentTime_2;
 }


 
 public static String getStringDate() {
  Date currentTime = new Date();
  SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
  String dateString = formatter.format(currentTime);
  return dateString;
 }


 
 public static String getStringDateShort() {
  Date currentTime = new Date();
  SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
  String dateString = formatter.format(currentTime);
  return dateString;
 }


 
 public static String getTimeShort() {
  SimpleDateFormat formatter = new SimpleDateFormat("HH:mm:ss");
  Date currentTime = new Date();
  String dateString = formatter.format(currentTime);
  return dateString;
 }


 
 public static Date strToDateLong(String strDate) {
  SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
  ParsePosition pos = new ParsePosition(0);
  Date strtodate = formatter.parse(strDate, pos);
  return strtodate;
 }


 
 public static String dateToStrLong(java.util.Date dateDate) {
  SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
  String dateString = formatter.format(dateDate);
  return dateString;
 }


 
 public static String dateToStr(java.util.Date dateDate) {
  SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
  String dateString = formatter.format(dateDate);
  return dateString;
 }


 
 public static Date strToDate(String strDate) {
  SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
  ParsePosition pos = new ParsePosition(0);
  Date strtodate = formatter.parse(strDate, pos);
  return strtodate;
 }


 
 public static Date getNow() {
  Date currentTime = new Date();
  return currentTime;
 }


 
 public static Date getLastDate(long day) {
  Date date = new Date();
  long date_3_hm = date.getTime() - 3600000 * 34 * day;
  Date date_3_hm_date = new Date(date_3_hm);
  return date_3_hm_date;
 }


 
 public static String getStringToday() {
  Date currentTime = new Date();
  SimpleDateFormat formatter = new SimpleDateFormat("yyyyMMdd HHmmss");
  String dateString = formatter.format(currentTime);
  return dateString;
 }


 
 public static String getHour() {
  Date currentTime = new Date();
  SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
  String dateString = formatter.format(currentTime);
  String hour;
  hour = dateString.substring(11, 13);
  return hour;
 }


 
 public static String getTime() {
  Date currentTime = new Date();
  SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
  String dateString = formatter.format(currentTime);
  String min;
  min = dateString.substring(14, 16);
  return min;
 }


 
 public static String getUserDate(String sformat) {
  Date currentTime = new Date();
  SimpleDateFormat formatter = new SimpleDateFormat(sformat);
  String dateString = formatter.format(currentTime);
  return dateString;
 }


 
 public static String getTwoHour(String st1, String st2) {
  String[] kk = null;
  String[] jj = null;
  kk = st1.split(":");
  jj = st2.split(":");
  if (Integer.parseInt(kk[0]) < Integer.parseInt(jj[0]))
   return "0";
  else {
   double y = Double.parseDouble(kk[0]) + Double.parseDouble(kk[1]) / 60;
   double u = Double.parseDouble(jj[0]) + Double.parseDouble(jj[1]) / 60;
   if ((y - u) > 0)
    return y - u + "";
   else
    return "0";
  }
 }


 
 public static String getTwoDay(String sj1, String sj2) {
  SimpleDateFormat myFormatter = new SimpleDateFormat("yyyy-MM-dd");
  long day = 0;
  try {
   java.util.Date date = myFormatter.parse(sj1);
   java.util.Date mydate = myFormatter.parse(sj2);
   day = (date.getTime() - mydate.getTime()) / (24 * 60 * 60 * 1000);
  } catch (Exception e) {
   return "";
  }
  return day + "";
 }


 
 public static String getPreTime(String sj1, String jj) {
  SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
  String mydate1 = "";
  try {
   Date date1 = format.parse(sj1);
   long Time = (date1.getTime() / 1000) + Integer.parseInt(jj) * 60;
   date1.setTime(Time * 1000);
   mydate1 = format.format(date1);
  } catch (Exception e) {
  }
  return mydate1;
 }


 
 public static String getNextDay(String nowdate, String delay) {
  try{
  SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
  String mdate = "";
  Date d = strToDate(nowdate);
  long myTime = (d.getTime() / 1000) + Integer.parseInt(delay) * 24 * 60 * 60;
  d.setTime(myTime * 1000);
  mdate = format.format(d);
  return mdate;
  }catch(Exception e){
   return "";
  }
 }


 
 public static boolean isLeapYear(String ddate) {


 
  Date d = strToDate(ddate);
  GregorianCalendar gc = (GregorianCalendar) Calendar.getInstance();
  gc.setTime(d);
  int year = gc.get(Calendar.YEAR);
  if ((year % 400) == 0)
   return true;
  else if ((year % 4) == 0) {
   if ((year % 100) == 0)
    return false;
   else
    return true;
  } else
   return false;
 }


 
 public static String getEDate(String str) {
  SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
  ParsePosition pos = new ParsePosition(0);
  Date strtodate = formatter.parse(str, pos);
  String j = strtodate.toString();
  String[] k = j.split(" ");
  return k[2] + k[1].toUpperCase() + k[5].substring(2, 4);
 }


 
 public static String getEndDateOfMonth(String dat) {// yyyy-MM-dd
  String str = dat.substring(0, 8);
  String month = dat.substring(5, 7);
  int mon = Integer.parseInt(month);
  if (mon == 1 || mon == 3 || mon == 5 || mon == 7 || mon == 8 || mon == 10 || mon == 12) {
   str += "31";
  } else if (mon == 4 || mon == 6 || mon == 9 || mon == 11) {
   str += "30";
  } else {
   if (isLeapYear(dat)) {
    str += "29";
   } else {
    str += "28";
   }
  }
  return str;
 }


 
 public static boolean isSameWeekDates(Date date1, Date date2) {
  Calendar cal1 = Calendar.getInstance();
  Calendar cal2 = Calendar.getInstance();
  cal1.setTime(date1);
  cal2.setTime(date2);
  int subYear = cal1.get(Calendar.YEAR) - cal2.get(Calendar.YEAR);
  if (0 == subYear) {
   if (cal1.get(Calendar.WEEK_OF_YEAR) == cal2.get(Calendar.WEEK_OF_YEAR))
    return true;
  } else if (1 == subYear && 11 == cal2.get(Calendar.MONTH)) {
   // 如果12月的最后一周横跨来年第一周的话则最后一周即算做来年的第一周
   if (cal1.get(Calendar.WEEK_OF_YEAR) == cal2.get(Calendar.WEEK_OF_YEAR))
    return true;
  } else if (-1 == subYear && 11 == cal1.get(Calendar.MONTH)) {
   if (cal1.get(Calendar.WEEK_OF_YEAR) == cal2.get(Calendar.WEEK_OF_YEAR))
    return true;
  }
  return false;
 }


 
 public static String getSeqWeek() {
  Calendar c = Calendar.getInstance(Locale.CHINA);
  String week = Integer.toString(c.get(Calendar.WEEK_OF_YEAR));
  if (week.length() == 1)
   week = "0" + week;
  String year = Integer.toString(c.get(Calendar.YEAR));
  return year + week;
 }


 
 public static String getWeek(String sdate, String num) {
  // 再转换为时间
  Date dd = VeDate.strToDate(sdate);
  Calendar c = Calendar.getInstance();
  c.setTime(dd);
  if (num.equals("1")) // 返回星期一所在的日期
   c.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
  else if (num.equals("2")) // 返回星期二所在的日期
   c.set(Calendar.DAY_OF_WEEK, Calendar.TUESDAY);
  else if (num.equals("3")) // 返回星期三所在的日期
   c.set(Calendar.DAY_OF_WEEK, Calendar.WEDNESDAY);
  else if (num.equals("4")) // 返回星期四所在的日期
   c.set(Calendar.DAY_OF_WEEK, Calendar.THURSDAY);
  else if (num.equals("5")) // 返回星期五所在的日期
   c.set(Calendar.DAY_OF_WEEK, Calendar.FRIDAY);
  else if (num.equals("6")) // 返回星期六所在的日期
   c.set(Calendar.DAY_OF_WEEK, Calendar.SATURDAY);
  else if (num.equals("0")) // 返回星期日所在的日期
   c.set(Calendar.DAY_OF_WEEK, Calendar.SUNDAY);
  return new SimpleDateFormat("yyyy-MM-dd").format(c.getTime());
 }


 
 public static String getWeek(String sdate) {
  // 再转换为时间
  Date date = VeDate.strToDate(sdate);
  Calendar c = Calendar.getInstance();
  c.setTime(date);
  // int hour=c.get(Calendar.DAY_OF_WEEK);
  // hour中存的就是星期几了，其范围 1~7
  // 1=星期日 7=星期六，其他类推
  return new SimpleDateFormat("EEEE").format(c.getTime());
 }
 public static String getWeekStr(String sdate){
  String str = "";
  str = VeDate.getWeek(sdate);
  if("1".equals(str)){
   str = "星期日";
  }else if("2".equals(str)){
   str = "星期一";
  }else if("3".equals(str)){
   str = "星期二";
  }else if("4".equals(str)){
   str = "星期三";
  }else if("5".equals(str)){
   str = "星期四";
  }else if("6".equals(str)){
   str = "星期五";
  }else if("7".equals(str)){
   str = "星期六";
  }
  return str;
 }


 
 public static long getDays(String date1, String date2) {
  if (date1 == null || date1.equals(""))
   return 0;
  if (date2 == null || date2.equals(""))
   return 0;
  // 转换为标准时间
  SimpleDateFormat myFormatter = new SimpleDateFormat("yyyy-MM-dd");
  java.util.Date date = null;
  java.util.Date mydate = null;
  try {
   date = myFormatter.parse(date1);
   mydate = myFormatter.parse(date2);
  } catch (Exception e) {
  }
  long day = (date.getTime() - mydate.getTime()) / (24 * 60 * 60 * 1000);
  return day;
 }


 
 public static String getNowMonth(String sdate) {
  // 取该时间所在月的一号
  sdate = sdate.substring(0, 8) + "01";


  // 得到这个月的1号是星期几
  Date date = VeDate.strToDate(sdate);
  Calendar c = Calendar.getInstance();
  c.setTime(date);
  int u = c.get(Calendar.DAY_OF_WEEK);
  String newday = VeDate.getNextDay(sdate, (1 - u) + "");
  return newday;
 }


 


 public static String getNo(int k) {


  return getUserDate("yyyyMMddhhmmss") + getRandom(k);
 }


 
 public static String getRandom(int i) {
  Random jjj = new Random();
  // int suiJiShu = jjj.nextInt(9);
  if (i == 0)
   return "";
  String jj = "";
  for (int k = 0; k < i; k++) {
   jj = jj + jjj.nextInt(9);
  }
  return jj;
 }


 
 public static boolean RightDate(String date) {


  SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
  ;
  if (date == null)
   return false;
  if (date.length() > 10) {
   sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
  } else {
   sdf = new SimpleDateFormat("yyyy-MM-dd");
  }
  try {
   sdf.parse(date);
  } catch (ParseException pe) {
   return false;
  }
  return true;
 }


 
 public static String getStringDateMonth(String sdate, String nd, String yf, String rq, String format) {
  Date currentTime = new Date();
  SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
  String dateString = formatter.format(currentTime);
  String s_nd = dateString.substring(0, 4); // 年份
  String s_yf = dateString.substring(5, 7); // 月份
  String s_rq = dateString.substring(8, 10); // 日期
  String sreturn = "";
  roc.util.MyChar mc = new roc.util.MyChar();
  if (sdate == null || sdate.equals("") || !mc.Isdate(sdate)) { // 处理空值情况
   if (nd.equals("1")) {
    sreturn = s_nd;
    // 处理间隔符
    if (format.equals("1"))
     sreturn = sreturn + "年";
    else if (format.equals("2"))
     sreturn = sreturn + "-";
    else if (format.equals("3"))
     sreturn = sreturn + "/";
    else if (format.equals("5"))
     sreturn = sreturn + ".";
   }
   // 处理月份
   if (yf.equals("1")) {
    sreturn = sreturn + s_yf;
    if (format.equals("1"))
     sreturn = sreturn + "月";
    else if (format.equals("2"))
     sreturn = sreturn + "-";
    else if (format.equals("3"))
     sreturn = sreturn + "/";
    else if (format.equals("5"))
     sreturn = sreturn + ".";
   }
   // 处理日期
   if (rq.equals("1")) {
    sreturn = sreturn + s_rq;
    if (format.equals("1"))
     sreturn = sreturn + "日";
   }
  } else {
   // 不是空值，也是一个合法的日期值，则先将其转换为标准的时间格式
   sdate = roc.util.RocDate.getOKDate(sdate);
   s_nd = sdate.substring(0, 4); // 年份
   s_yf = sdate.substring(5, 7); // 月份
   s_rq = sdate.substring(8, 10); // 日期
   if (nd.equals("1")) {
    sreturn = s_nd;
    // 处理间隔符
    if (format.equals("1"))
     sreturn = sreturn + "年";
    else if (format.equals("2"))
     sreturn = sreturn + "-";
    else if (format.equals("3"))
     sreturn = sreturn + "/";
    else if (format.equals("5"))
     sreturn = sreturn + ".";
   }
   // 处理月份
   if (yf.equals("1")) {
    sreturn = sreturn + s_yf;
    if (format.equals("1"))
     sreturn = sreturn + "月";
    else if (format.equals("2"))
     sreturn = sreturn + "-";
    else if (format.equals("3"))
     sreturn = sreturn + "/";
    else if (format.equals("5"))
     sreturn = sreturn + ".";
   }
   // 处理日期
   if (rq.equals("1")) {
    sreturn = sreturn + s_rq;
    if (format.equals("1"))
     sreturn = sreturn + "日";
   }
  }
  return sreturn;
 }


 public static String getNextMonthDay(String sdate, int m) {
  sdate = getOKDate(sdate);
  int year = Integer.parseInt(sdate.substring(0, 4));
  int month = Integer.parseInt(sdate.substring(5, 7));
  month = month + m;
  if (month < 0) {
   month = month + 12;
   year = year - 1;
  } else if (month > 12) {
   month = month - 12;
   year = year + 1;
  }
  String smonth = "";
  if (month < 10)
   smonth = "0" + month;
  else
   smonth = "" + month;
  return year + "-" + smonth + "-10";
 }


 public static String getOKDate(String sdate) {
  if (sdate == null || sdate.equals(""))
   return getStringDateShort();


  if (!VeStr.Isdate(sdate)) {
   sdate = getStringDateShort();
  }
  // 将“/”转换为“-”
  sdate = VeStr.Replace(sdate, "/", "-");
  // 如果只有8位长度，则要进行转换
  if (sdate.length() == 8)
   sdate = sdate.substring(0, 4) + "-" + sdate.substring(4, 6) + "-" + sdate.substring(6, 8);
  SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
  ParsePosition pos = new ParsePosition(0);
  Date strtodate = formatter.parse(sdate, pos);
  String dateString = formatter.format(strtodate);
  return dateString;
 }


 public static void main(String[] args) throws Exception {
  try {
   //System.out.print(Integer.valueOf(getTwoDay("2006-11-03 12:22:10", "2006-11-02 11:22:09")));
  } catch (Exception e) {
   throw new Exception();
  }
  //System.out.println("sss");
 }