Java日期的相关操作

1.获取当前时间的前一个月

Date current = new Date();

Calendar cldCurrent = Calendar.getInstance(java.util.TimeZone.getTimeZone("GMT+8:00"));

cldCurrent.setTime(current);

cldCurrent.add(Calendar.MONTH, -Integer.parseInt(monthnum));

Date LastDay = cldCurrent.getTime();

2.将8位或12位或14位的数值型日期时间转换为10位或16位或19带格式的日期时间。 型如： 20040101 转换为 2004/01/01，或 200401010101 转换为 2004/01/01 01:01，或 20040101010101 转换为 2004/01/01 01:01:01。

输入参数：Long date 十二位或十四位的数字日期时间。 返回参数：String fmDate 16位或19位带格式的日期

public static String getStrFmDate(Long date) {

String fmDate = new String();

if (date == null) {

fmDate = "";

}

else {

fmDate = date.toString();

String year = "";

String month = "";

String day = "";

String hour = "";

String minute = "";

//日期格式不合法则转化为空串

if (fmDate.length() < 8) {

fmDate = "";

}

if (fmDate.length() >= 8) {

year = fmDate.substring(0, 4);

month = fmDate.substring(4, 6);

day = fmDate.substring(6, 8);

fmDate = year + "/" + month + "/" + day;

}

if ( (date.toString()).length() >= 12) {

hour = (date.toString()).substring(8, 10);

minute = (date.toString()).substring(10, 12);

fmDate = fmDate + " " + hour + ":" + minute;

}

if ( (date.toString()).length() == 14) {

fmDate = fmDate + ":" + (date.toString()).substring(12, 14);

}

}

return fmDate;

}

3.获取当前系统时间

/**

* 功能：得到系统当前时间显示，格式：yyyy/mm/dd hh:mm主要是为页面显示用

* 输入参数：

* 返回参数：String:系统当前时间

*/

public static String getCurrentDateTimeView() {

//获得当前日期

Calendar cldCurrent = Calendar.getInstance(java.util.TimeZone.getTimeZone(

"GMT+8:00"));

//获得年月日

String strYear = String.valueOf(cldCurrent.get(Calendar.YEAR));

String strMonth = String.valueOf(cldCurrent.get(Calendar.MONTH) + 1);

String strDate = String.valueOf(cldCurrent.get(Calendar.DATE));

String srtHours = String.valueOf(cldCurrent.get(Calendar.HOUR_OF_DAY));

String strMinute = String.valueOf(cldCurrent.get(Calendar.MINUTE));

//整理格式

if (strMonth.length() < 2) {

strMonth = "0" + strMonth;

}

if (strDate.length() < 2) {

strDate = "0" + strDate;

}

if (srtHours.length() < 2) {

srtHours = "0" + srtHours;

}

if (strMinute.length() < 2) {

strMinute = "0" + strMinute;

}

//得出当天日期时间的字符串

String StrCurrentCalendar = strYear + "/" + strMonth + "/" + strDate +

" "

+ srtHours + ":" + strMinute;

return StrCurrentCalendar;

}