Time tool class, get the current time, date to string

package com.qiu.tool;

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

public class DateTools {
    private static final String YYYY_MM_DD="yyyy-MM-dd";
    private static final String YYYY_MM_DD_HH="yyyy-MM-dd HH";
    private static final String HH="HH";
    private static final String HH_MM="HH:mm";
    private static final String HH_MM_SS="HH:mm:ss";
    private static final String HH_MM_SS_A="HH:mm:ss a";
    private static final String YYYY_MM_DD_HH_MM="yyyy-MM-dd HH:mm";
    private static final String YYYY_MM_DD_HH_MM_SS="yyyy-MM-dd HH:mm:ss";
    private static final String YYYY_MM_DD_HH_MM_SS_A="yyyy-MM-dd HH:mm:ss a";

    /**
     *  Get the current time 
     * @param pattern  Format ：
     *                --yyyy-MM-dd;
     *                --yyyy-MM-dd HH;
     *                --HH;
     *                --HH:mm;
     *                --HH:mm:ss;
     *                --HH:mm:ss a;
     *                --yyyy-MM-dd HH:mm;
     *                --yyyy-MM-dd HH:mm:ss;
     *                --yyyy-MM-dd HH:mm:ss a
     * @return  Current time string 
     */
    public static String getNowTime(String pattern){
        SimpleDateFormat sdf = new SimpleDateFormat(pattern);
        Date date = new Date();
        return sdf.format(date);
    }

    /**
     *  Get the current time ( from Calendar Class gets )
     * @param pattern  Format ：
     *                 --yyyy-MM-dd;
     *                 --yyyy-MM-dd HH;
     *                 --HH;
     *                 --HH:mm;
     *                 --HH:mm:ss;
     *                 --HH:mm:ss a;
     *                 --yyyy-MM-dd HH:mm;
     *                 --yyyy-MM-dd HH:mm:ss;
     *                 --yyyy-MM-dd HH:mm:ss a;
     *                 --yyyy year MM month dd HH when mm branch ss second ;
     * @return  Current time string 
     */
    public static String getNowTimeFormCalendar(String pattern) {
        Calendar calendar = Calendar.getInstance();
        SimpleDateFormat sdf = new SimpleDateFormat(pattern);
        return sdf.format(calendar.getTime());
    }

    /**
     *  Get the current time ( from Calendar Class gets , Count year, month, day, hour, minute and second )
     * @param pattern  Format ：
     *                --yyyy-MM-dd;
     *                --yyyy-MM-dd HH;
     *                --HH;
     *                --HH:mm;
     *                --HH:mm:ss;
     *                --HH:mm:ss a;
     *                --yyyy-MM-dd HH:mm;
     *                --yyyy-MM-dd HH:mm:ss;
     *
     * @return  Current time string 
     */
    public static String getNowTimeForamCalendarCount(String pattern){
        Calendar cal=Calendar.getInstance();
        StringBuilder sb=new StringBuilder("");
        if(pattern.contains("yyyy")){
            sb.append(cal.get(Calendar.YEAR));
            sb.append(" year ");
        }
        if(pattern.contains("MM")){
            sb.append(cal.get(Calendar.MONTH));
            sb.append(" month ");
        }
        if(pattern.contains("dd")){
            sb.append(cal.get(Calendar.DATE));
            sb.append(" Japan ");
        }

        if(pattern.contains("HH")){
            sb.append(cal.get(Calendar.HOUR_OF_DAY));
            sb.append(" when ");
        }
        if(pattern.contains("mm")){
            sb.append(cal.get(Calendar.MINUTE));
            sb.append(" branch ");
        }
        if(pattern.contains("ss")){
            sb.append(cal.get(Calendar.SECOND));
            sb.append(" second ");
        }
        return  sb.toString();
    }



    /**
     *  Get a few days 
     * @param number  Days 
     * @return  A few days later 
     */
    public static Date getDateDaysAfter(int number){
        return getDateAround(+number,Calendar.DATE);
    }

    /**
     *  Get a few days ago 
     * @param number  Days 
     * @return  A few days ago 
     */
    public static Date getDateDaysBefore(int number){
       return getDateAround(-number,Calendar.DATE);
    }

    /**
     *  Get a few months later 
     * @param number  Monthly number 
     * @return  A few months later 
     */
    public static Date getDateMonthAfter(int number){
        return getDateAround(+number,Calendar.MONTH);
    }

    /**
     *  Get the time a few months ago 
     * @param number  Monthly number 
     * @return  A few months ago 
     */
    public static Date getDateMonthBefore(int number){
        return getDateAround(-number,Calendar.MONTH);
    }

    /**
     *  Get a few years later 
     * @param number  number of years 
     * @return  A few years later 
     */
    public static Date getDateYearAfter(int number){
        return getDateAround(+number,Calendar.YEAR);
    }

    /**
     *  Get the time a few years ago 
     * @param number  number of years 
     * @return  A few years ago 
     */
    public static Date getDateYearBefore(int number){
        return getDateAround(-number,Calendar.YEAR);
    }

    /**
     *
     * @param number  Positive number is plus , Negative is minus 
     * @param dateUnit  Time single temperature ：
     *                 --Calendar.YEAR  year ;
     *                 --Calendar.MONTH  month ;
     *                 --Calendar.DATE  Japan ;
     *                 --Calendar.HOUR  when ;
     *                 --Calendar.MINUTE  branch ;
     *
     * @return
     */
    private static Date getDateAround(int number,int dateUnit){
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(new Date());
        calendar.add(dateUnit, number);
        return calendar.getTime();
    }

    /**
     * date Time to format 
     * @param date  date data 
     * @param pattern  Format 
     * @return   Formatted time string 
     */
    public  static String dateToFormatString(Date date,String pattern){
        SimpleDateFormat sdf = new SimpleDateFormat(pattern);
        String format = sdf.format(date.getTime());
        return format;
    }

}