java处理日期时间的方法

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.*;

public class DateUtils {
public static void main(String[] args) throws ParseException {
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
String str = "2012-05-02";
Date date = df.parse(str);
Map<String, String> map = getFirstday_Lastday_Month(date);
System.out.println("当月第一天：" + getFirstDay());//两种方式getFirstDay()，getFirstDay1()
System.out.println("当月最后一天：" + getLastDay());//同
System.out.println("月最后一天：" + getLastDay());//同

System.out.println("一个月前第一天：" + map.get("first"));
System.out.println("一个月前最后一天：" + map.get("last"));

System.out.println("获取前一个月的第一天：" + getPreMonthFirstDay());
System.out.println("获取前一个月的最后一天：" +getPreMonthLastDay());

Calendar calendar = new GregorianCalendar();
calendar.setTime(date); //放入你的日期
System.out.println("天数为=" + calendar.getActualMaximum(Calendar.DAY_OF_MONTH));
}

/**
* 计算两个日期相差的月份数
*
* @param date1   日期1
* @param date2   日期2
* @param pattern 日期1和日期2的日期格式
* @return 相差的月份数
* @throws ParseException
*/
public static int countMonths(String date1, String date2, String pattern) throws ParseException {
SimpleDateFormat sdf = new SimpleDateFormat(pattern);

Calendar c1 = Calendar.getInstance();
Calendar c2 = Calendar.getInstance();

c1.setTime(sdf.parse(date1));
c2.setTime(sdf.parse(date2));

int year = c2.get(Calendar.YEAR) - c1.get(Calendar.YEAR);

//开始日期若小于结束日期
if (year < 0) {
year = -year;
return year * 12 + c1.get(Calendar.MONTH) - c2.get(Calendar.MONTH);
}

return year * 12 + c2.get(Calendar.MONTH) - c1.get(Calendar.MONTH) + 1;
}

//获取当前月第一天：方式一
private static String getFirstDay() {
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
Calendar calendar = Calendar.getInstance();
Date theDate = calendar.getTime();

GregorianCalendar gcLast = (GregorianCalendar) Calendar.getInstance();
gcLast.setTime(theDate);
gcLast.set(Calendar.DAY_OF_MONTH, 1);
String day_first = df.format(gcLast.getTime());
StringBuffer str = new StringBuffer().append(day_first).append(" 00:00:00");
return str.toString();
}

//获取当前月第一天：方式二
private static String getFirstDay1() {
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
Calendar c = Calendar.getInstance();
c.add(Calendar.MONTH, 0);
c.set(Calendar.DAY_OF_MONTH, 1);//设置为1号,当前日期既为本月第一天
String first_Day_Of_Month = df.format(c.getTime());
return first_Day_Of_Month;
}

//获取当月最后一天:方式一
private static String getLastDay() {
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
Calendar calendar = Calendar.getInstance();
Date theDate = calendar.getTime();
String s = df.format(theDate);
StringBuffer str = new StringBuffer().append(s).append(" 23:59:59");
return str.toString();

}

//获取当前月最后一天:方式二
private static String getLastDay1() {
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
Calendar ca = Calendar.getInstance();
ca.set(Calendar.DAY_OF_MONTH, ca.getActualMaximum(Calendar.DAY_OF_MONTH));
String lastDay = df.format(ca.getTime());
return lastDay;
}

//获取前月的第一天
private static String getPreMonthFirstDay() {
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
Calendar cal_1 = Calendar.getInstance();//获取当前日期
cal_1.add(Calendar.MONTH, -1);
cal_1.set(Calendar.DAY_OF_MONTH, 1);//设置为1号,当前日期既为本月第一天
String firstDay = df.format(cal_1.getTime());
return firstDay;
}

//获取前月的最后一天
private static String getPreMonthLastDay() {
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
Calendar cale = Calendar.getInstance();
cale.set(Calendar.DAY_OF_MONTH, 0);//设置为1号,当前日期既为本月第一天
String lastDay = df.format(cale.getTime());
System.out.println("-----2------lastDay:" + lastDay);
return lastDay;
}
/**
* 某一个月第一天和最后一天
*/
private static Map<String, String> getFirstday_Lastday_Month(Date date) {
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
calendar.add(Calendar.MONTH, -1);
Date theDate = calendar.getTime();

//上个月第一天
GregorianCalendar gcLast = (GregorianCalendar) Calendar.getInstance();
gcLast.setTime(theDate);
gcLast.set(Calendar.DAY_OF_MONTH, 1);
String day_first = df.format(gcLast.getTime());
StringBuffer str = new StringBuffer().append(day_first).append(" 00:00:00");
day_first = str.toString();

//上个月最后一天
calendar.add(Calendar.MONTH, 1);    //加一个月
calendar.set(Calendar.DATE, 1);        //设置为该月第一天
calendar.add(Calendar.DATE, -1);    //再减一天即为上个月最后一天
String day_last = df.format(calendar.getTime());
StringBuffer endStr = new StringBuffer().append(day_last).append(" 23:59:59");
day_last = endStr.toString();

Map<String, String> map = new HashMap<String, String>();
map.put("first", day_first);
map.put("last", day_last);
return map;
}

public static List<String> getMonthBetween(String minDate, String maxDate) throws ParseException {
ArrayList<String> result = new ArrayList<String>();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM");//格式化为年月

Calendar min = Calendar.getInstance();
Calendar max = Calendar.getInstance();

min.setTime(sdf.parse(minDate));
min.set(min.get(Calendar.YEAR), min.get(Calendar.MONTH), 1);

max.setTime(sdf.parse(maxDate));
max.set(max.get(Calendar.YEAR), max.get(Calendar.MONTH), 2);

Calendar curr = min;
while (curr.before(max)) {
result.add(sdf.format(curr.getTime()));
curr.add(Calendar.MONTH, 1);
}

return result;
}

//获取某一日期的哪一天
public static int getDayOfMonth(String nowDate) {
Calendar c = Calendar.getInstance();//获得一个日历的实例
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
Date date = null;
try {
date = sdf.parse(nowDate);//初始日期
} catch (Exception e) {

}
c.setTime(date);//设置日历时间
return c.get(Calendar.DAY_OF_MONTH);
}

public static String dateFormatToString(Date date, String formatString) {
java.text.SimpleDateFormat formatter = new SimpleDateFormat(formatString);

return formatter.format(date);//格式化数据
}

public static Date dateFormatToDate(String date) throws ParseException {
java.text.SimpleDateFormat formatter =  new SimpleDateFormat("yyyy-MM-dd ");
return formatter.parse(date);
}

public static int compare_date(String nowDATE, String endDATE) {
DateFormat df = new SimpleDateFormat("yyyy-MM-dd");
try {
Date dt1 = df.parse(nowDATE);
Date dt2 = df.parse(endDATE);
if (dt1.getTime() > dt2.getTime()) {
//System.out.println("dt1 在dt2前");
return 1;
} else if (dt1.getTime() < dt2.getTime()) {
//System.out.println("dt1在dt2后");
return -1;
} else {
return 0;
}
} catch (Exception exception) {
exception.printStackTrace();
}
return 0;
}

public static int getMonthToDay(String date) throws ParseException {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
Calendar calendar = new GregorianCalendar();
Date date1 = sdf.parse(date);
calendar.setTime(date1); //放入你的日期
return calendar.getActualMaximum(Calendar.DAY_OF_MONTH);
}

//获取当前时间的年和月：
public int getCurrentYearAndMonth() throws ParseException {
SimpleDateFormat formatter = new SimpleDateFormat("yyyyMM");
Date date = new Date();
String currentYearAndMonth = formatter.format(date);
int currentDate = Integer.parseInt(currentYearAndMonth);
return currentDate;
}

//======================================比较两个日期相差的天数 ================================================
//（版本1）：根据您输入的小时与分不同，返回不同的结果的，
// 比如你输入的参数今天中午与昨天晚上的两个时间，它就会告诉你相差0天
public static int getIntervalDays(Date fDate, Date oDate) {
if (null == fDate || null == oDate) {
return -1;
}
long intervalMilli = oDate.getTime() - fDate.getTime();
return (int) (intervalMilli / (24 * 60 * 60 * 1000));
}

//（版本2）
public static int daysBetween(Date smdate,Date bdate) throws ParseException{
SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");
smdate=sdf.parse(sdf.format(smdate));
bdate=sdf.parse(sdf.format(bdate));
Calendar cal = Calendar.getInstance();
cal.setTime(smdate);
long time1 = cal.getTimeInMillis();
cal.setTime(bdate);
long time2 = cal.getTimeInMillis();
long between_days=(time2-time1)/(1000*3600*24);
return Integer.parseInt(String.valueOf(between_days));
}

//（版本3）：你输入的参数今天中午与昨天晚上的两个时间，只关心天，因此输出的结果是1
public static int daysOfTwo(Date fDate, Date oDate) {
Calendar aCalendar = Calendar.getInstance();
aCalendar.setTime(fDate);
int day1 = aCalendar.get(Calendar.DAY_OF_YEAR);
aCalendar.setTime(oDate);
int day2 = aCalendar.get(Calendar.DAY_OF_YEAR);
return day2 - day1;
}
//======================================================================================