Java DateUtil Time Daquan

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.TimeZone;
 
/**
* author zys
*/
public class DateUtil{
     
    /**定义常量**/
    public static final String DATE_JFP_STR="yyyyMM";
    public static final String DATE_FULL_STR = "yyyy-MM-dd HH:mm:ss";
    public static final String DATE_SMALL_STR = "yyyy-MM-dd";
    public static final String DATE_KEY_STR = "yyyyMMddHHmmss";
    public static SimpleDateFormat sdf = new SimpleDateFormat(DATE_FULL_STR);
   
    //获取年月日时
    public static String getyyyyMMddHHmmss(){
    SimpleDateFormat df = new SimpleDateFormat(DATE_KEY_STR);
      return df.format(new Date());
    }
    /**
     * 获取当天的开始时间
     * @return
     */
    private static Date getTodayStartTime() { 
        Calendar todayStart = Calendar.getInstance(); 
        todayStart.set(Calendar.HOUR, 0); 
        todayStart.set(Calendar.MINUTE, 0); 
        todayStart.set(Calendar.SECOND, 0); 
        todayStart.set(Calendar.MILLISECOND, 0); 
        return todayStart.getTime(); 
    } 
    /**
     * 获取当天的结束时间
     * @return
     */
    private static Date getTodayEndTime() { 
        Calendar todayEnd = Calendar.getInstance(); 
        todayEnd.set(Calendar.HOUR, 23); 
        todayEnd.set(Calendar.MINUTE, 59); 
        todayEnd.set(Calendar.SECOND, 59); 
        todayEnd .set(Calendar.MILLISECOND, 999); 
        return todayEnd.getTime(); 
    } 
    /**
     * yyyy-MM-dd HH:mm:ss
     * extract string date using preset format
     * @param strDate date string
     * @ return
     */
    public static Date parse(String strDate) {
        return parse(strDate,DATE_FULL_STR);
    }
     
    /**
     * Extract string date using user format
     * @param strDate date string
     * @param pattern date format
     * @return
     */
    public static Date parse(String strDate, String pattern) {
    if(pattern==null||pattern.equals("")){
    pattern =DATE_FULL_STR ;
    }
        SimpleDateFormat df = new SimpleDateFormat(pattern);
        try {
            return df.parse(strDate);
        } catch (ParseException e) {
            e.printStackTrace();
            return null;
        }
    }
    /**
* Get dates in months
*
* @param date date
* @param afterMonth month number
* @return date Date
*/
public static Date getAfterMonth(Date date, int afterMonth) {
if (date == null)
date = new Date();

GregorianCalendar cal = new GregorianCalendar();
cal.setTime(date);

cal.add(java.util.Calendar.MONTH, afterMonth);
return cal.getTime();
}

    /**
     * 取得指定日期几天前的日期
     *
     * @param date 日期
     * @param beforeDays 天数(大于0)
     * @return 日期
     */
    public static Date getBeforeDay(Date date, int beforeDays) {
        if (date == null)
            date = new Date();
        GregorianCalendar cal = new GregorianCalendar();
        cal.setTime(date);
        cal.add(java.util.Calendar.DATE, 0 - Math.abs(beforeDays));
        return cal.getTime();
    }
    /**
* Get the date a few days after the specified date
*
* @param date date
* @ param afterDays number of days
* @return date
*/
public static Date getAfterDay(Date date, int afterDays) {
if (date == null)
date = new Date();

GregorianCalendar cal = new GregorianCalendar();
cal.setTime(date);
cal.add(java.util.Calendar.DATE, afterDays);
return cal.getTime();
}
    /**
* Get the time after n minutes
*
* @param date Date
* @param afterMins
* @return Time Timestamp
*/
public static Date getAfterMinute(Date date, long afterMins) {
if (date == null)
date = new Date();

long longTime = date.getTime() + afterMins * 60 * 1000;

return new Date(longTime);
}
  /**
* 取得n分钟之前的时间
*
* @param date 日期
* @param afterMins
* @return 时间Timestamp
*/
public static Date getBeforeMinute(Date date, long afterMins) {
if (date == null)
date = new Date();

long longTime = date.getTime() - afterMins * 60 * 1000;

return new Date(longTime);
}
    /**
     * 两个时间比较
     * @param date
     * @return
     */
    public static int compareDateWithNow(Date date1){
        Date date2 = new Date();
        int rnum =date1.compareTo(date2);
        return rnum;
    }
     
    /**
     * 两个时间比较(时间戳比较)
     * @param date
     * @return
     */
    public static int compareDateWithNow(long date1){
        long date2 = dateToUnixTimestamp();
        if(date1>date2){
            return 1;
        }else if(date1<date2){
            return -1;
        }else{
            return 0;
        }
    }
    /**
     * Get the current time of the system + generate a 5-digit random number
     * @return
     */
    public static String getCurrentTime() {
        SimpleDateFormat df = new SimpleDateFormat(DATE_KEY_STR);
// return df.format(new Date())+(int)(( Math.random()*9+1)*10000);
        return df.format(new Date());
    }
    /**
     * Get the current system time
     * @return
     */
    public static String getNowTime() {
        SimpleDateFormat df = new SimpleDateFormat(DATE_FULL_STR);
        return df.format(new Date());
    }
    /**
     * Get the current date type of the system
     * @return
     */
    public static Date getNowTimeDate() {
        SimpleDateFormat df = new SimpleDateFormat(DATE_FULL_STR);
        try {
return df.parse(df.format(new Date()));
} catch (ParseException e) {
// TODO Auto-generated catch block
e .printStackTrace();
}
        return null;
    }
    /**
     * Get the current system time according to your own format
     * @return
     */
    public static String getNowTime(String type) {
        SimpleDateFormat df = new SimpleDateFormat(type);
        return df.format(new Date());
    }
    /**
* Convert Date to string yyyy-MM-dd HH:mm:ss
*
* @param Date
* @return String
*/
public static String formatDate(Date date) {
if (date == null) {
return "";
}
return sdf.format(date);
}
    /**
     * Get the current billing period of the system
     * @return
     */
    public static String getJFPTime() {
        SimpleDateFormat df = new SimpleDateFormat(DATE_JFP_STR);
        return df.format(new Date());
    }
     
    /**
     * Convert the specified date to a Unix timestamp
     * @param String date needs to be converted date yyyy-MM-dd HH:mm:ss
     * @return long timestamp
     */
    public static long dateToUnixTimestamp(String date) {
        long timestamp = 0;
        try {
            timestamp = new SimpleDateFormat(DATE_FULL_STR).parse(date).getTime();
        } catch (ParseException e) {
            e.printStackTrace();
        }
        return timestamp;
    }
     
    /**
     * Convert the specified date to a Unix timestamp
     * @param String date The date to be converted yyyy-MM-dd
     * @return long timestamp
     */
    public static long dateToUnixTimestamp(String date, String dateFormat) {
        long timestamp = 0;
        try {
            timestamp = new SimpleDateFormat(dateFormat).parse (date).getTime();
        } catch (ParseException e) {
            e.printStackTrace();
        }
        return timestamp;
    }
     
    /**
     * Convert current date to Unix timestamp
     * @return long timestamp
     */
    public static long dateToUnixTimestamp() {
        long timestamp = new Date().getTime();
        return timestamp;
    }
     
     
    /* *
     * Convert Unix timestamp to date
     * @param long timestamp timestamp
     * @return String date string
     */
    public static String unixTimestampToDate(long timestamp) {
        SimpleDateFormat sd = new SimpleDateFormat(DATE_FULL_STR);
        sd.setTimeZone(TimeZone.getTimeZone ("GMT+8"));
        return sd.format(new Date(timestamp));
    }
   
   
    /**
     * Add a few hours to the time
     * @param day Current time format: yyyy-MM-dd HH:mm:ss
     * @param hour the time to be added
     * @return
     */
    public static String addDateMinut(String day , int hour){  
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        Date date = null;  
        try {  
            date = format.parse(day);  
        } catch (Exception ex) {  
            ex. printStackTrace();  
        }  
        if (date == null)  
            return "";  
        System.out.println("front:" + format.format(date)); //Display the entered date 
        Calendar cal = Calendar.getInstance();  
        cal.setTime(date);  
        cal.add(Calendar.HOUR, hour);// 24-hour 
        date = cal.getTime();  
        System.out.println("after:" + format.format(date)); //display the updated date
        cal = null;  
        return format.format(date);  

    }
}