日期工具类

转自 http://www.iteye.com/topic/235843
public class SfUtil {
    public static final long hour = 60*60*1000l;            //一个小时

    public static final long oneday = 24*hour;              //一天


    public static String el(String str,int len){
        if(str==null) return "";
        if(len == -1) return str;
        if(str.length()<=len) return str;
        if(str.length()>len) return str.substring(0,len);
        return "";
    }

    /**
      * 显示按键
      * @param list
      * @return string
      */
     public String getButtom(List list){
         String button = "";
         for(int i=0;i<list.size();i++){
             Object[] obj = (Object[])list.get(i);
             button += htmlButton(obj) + "&nbsp;&nbsp";
         }
         return button;
     }

    private String htmlButton(Object[] obj){
         StringBuffer button = new StringBuffer();
         button.append("<input type=\"button\" name="+obj[0]+" value="+obj[1]+" onclick="+obj[2]+" id="+obj[3]+" ");
         button.append(" class=\"button\" onmousedown=\"this.className='button_down'\" onmouseout=\"if(this.className!='button') this.className='button';\" ");
         button.append(" onmouseover=\"if(this.className!='button_over') this.className='button_over';\" onfocus=\"this.blur();\">");
         return button.toString();
     }

    /**
     * 转为时间格式
     * @param dateStr  2007-10-3 20:00
     * @param format   yyyy-MM-dd HH:mm
     * @return  date
     */
    public static Date stringToDate(String dateStr,String format){
        java.text.SimpleDateFormat sf = new SimpleDateFormat(format);
        try {
            Date date = sf.parse(dateStr);
            return date;
        } catch (ParseException e) {
            return null;
        }
    }

    public static Timestamp stringToTimestamp(String dateStr,String format){
        if(format==null) format="yyyy-MM-dd HH:mm";
        Date date =  stringToDate(dateStr,format);
        return new Timestamp(date.getTime());
    }


    //取出上个月的当前时间
    public static Timestamp getlastMonthday(Timestamp time){
        Calendar c = Calendar.getInstance();
        c.setTimeInMillis(time.getTime());
        c.set(Calendar.DAY_OF_MONTH,c.get(Calendar.DAY_OF_MONTH)==31?c.get(Calendar.DAY_OF_MONTH)-1:c.get(Calendar.DAY_OF_MONTH));
        c.set(Calendar.MONTH,c.get(Calendar.MONTH)-1);

        return new Timestamp(c.getTime().getTime());
    }

    /**
     * 时间判断
     * @param t1    当前时间
     * @param t2    规写时间
     * @param day   天数
     * @return      boolean
     */
    public static boolean checkTimeBeweet(Timestamp t1,Timestamp t2,int day){
        long daylong = 24*hour;                   //一天时间
        long longt1 = t1.getTime();
        long longt2 = t2.getTime();
        System.out.println(""+(Math.abs(longt2-longt1)-daylong*day));

        return Math.abs(longt2-longt1)-daylong*day>0;
    }


    /**
     *转换为时间格式
     * @param time
     * @param i
     * @return  string
     */
   public static String getDateFormat(Timestamp time,int i){
       if(time==null) return "";
       String format = "yyyy-MM-dd";
       switch(i){
           case 1:format="yyyy-MM-dd";break;
           case 2:format="yyyy-MM-dd HH:mm";break;
           case 3:format="HH点mm分";break;
           case 4:format="yyyy年MM月dd日 HH点mm分";break;
           case 5:format="yyyyMMdd";break;
           case 6:format="yyyy年MM月dd日";break;
           case 7:format="yyyyMMdd";break;
           case 8:format="MM月dd日 HH点mm分";break;
           case 9:format="MM-dd HH:mm";break;
           case 10:format="MM月dd日";break;
           case 11:format=" HH:mm";break;
           case 12:format="yyyy";break;
           case 13:format="MM-dd";break;
           case 14:format="yyyyMM";break;
           case 15:format="yyyy-MM-dd hh:mm";break;
           case 16:format="yy-MMdd hh:mm";break;
           case 17:format="yyyyMMddHH";break;
           case 18:format="HH";break;
           default: format = "yyyy-MM-dd";break;
       }
       SimpleDateFormat sdf = new SimpleDateFormat(format);
font-size: 1em; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 38px; padding-top: 0p